While the NFL draft isn't exactly a guessing game, it can be difficult for teams to know exactly what they're getting in a prospect.

How do the skills the player honed in college translate to the NFL? What kind of roles can the draftee fill? There's no concrete way to answer these questions—unless there's a team out there with a time machine—but pro-player comparisons can provide a starting point.

Saquon Barkley, for example, drew comparisons to Ezekiel Elliott and even Barry Sanders heading into last year's draft, and he had an Elliott-like impact on the New York Giants offense as a rookie.

Here, you'll find pro-player comparisons for the top 12 prospects on Bleacher Report draft analyst Matt Miller's big board.

1. Quinnen Williams, DT, Alabama

Player Comp: Grady Jarrett

If you want a player who can disrupt the backfield from the defensive interior, Alabama's Quinnen Williams is your guy. Like Atlanta Falcons standout Grady Jarrett, he has the strength, savvy and quick first step needed to wreck plays in both the running and passing games.

Last season, Williams racked up 71 tackles, 19.5 tackles for a loss and 8.0 sacks.

"His swim move is deadly, and he has good eyes as he finds the ball well," Yahoo's Terez Paylor wrote. "Williams might be the best player in the entire draft, and he's a Day 1 starter with All-Pro potential."

Selecting an edge-rusher usually makes for a draft-day splash, but adding Williams should also give a team an impact defender for the next decade-plus.      

2. Nick Bosa, EDGE, Ohio State

Player Comp: Joey Bosa

There's no reason to overthink this one. Ohio State's Nick Bosa compares favorably to his older brother, Joey, both in terms of physical makeup and skill set. Nick is a powerful rusher off the edge and has a variety of moves and countermoves with which to win blocking matchups.

The younger Bosa, 21, measured just a shade shorter than his 23-year-old sibling (6'4" vs. 6'5") but also ran a slightly faster 40-yard dash (4.79 vs. 4.86 seconds) at the scouting combine.

There's no guarantee that Nick will produce double-digit sacks as a rookie like his brother did in 2016, of course. However, if he lands in an aggressive system with an established pass-rusher opposite him—like Joey did in San Diego with Melvin Ingram—the potential is there.

3. Josh Allen, EDGE, Kentucky

Player Comp: Bradley Chubb

You know it's a strong defensive draft when the No. 2 pass-rusher compares to last year's top rookie sack artist. This is the case with Kentucky's Josh Allen, who plays a lot like 2018's No. 5 pick, Bradley Chubb.

Both Chubb and Allen have shown the ability to win off the edge with pure speed, but neither is strictly a speed rusher. Each has a powerful frame—Chubb is 6'4", 269 pounds, while Allen is 6'5", 262 pounds—that allows them to battle stronger blockers at the point of attack.

Allen can fill in as an edge-rushing linebacker in a 3-4, as Chubb did for the Denver Broncos as a rookie, but he can also play defensive end in a 4-3 base defense. Either way, it wouldn't be a shock to see Allen mirror Chubb and produce double-digit sacks as a rookie.

4. Devin White, LB, LSU

Player Comp: Myles Jack

LSU linebacker Devin White might be on the shorter side (6'0"), but with his 237-pound frame, it wouldn't be fair to call him small. It definitely wouldn't be fair to call him slow after he ran a blazing 4.42-second 40 at the scouting combine.

A slightly undersized linebacker with cornerback speed and elite instincts? That sounds a lot like the Jacksonville Jaguars' Myles Jack, who has amassed 197 tackles over the past two seasons.

Like Jack, White is capable of racking up tackles. The former Tiger had 123 in 2018 alone. He is a true three-down linebacker who can chase ball-carriers, cover receivers at the second level and make impact plays when called upon.

5. T.J. Hockenson, TE, Iowa

Player Comp: Zach Ertz

Zach Ertz has emerged as a legitimate No. 1 target for the Philadelphia Eagles over the last couple of seasons, and that's exactly the kind of weapon Iowa's T.J. Hockenson can be—even early in his career.

"A near-perfect prospect, Hockenson is a three-down tight end who can block and open up the receiving game; looking like a 10-year veteran while coming out of Iowa as a redshirt sophomore," Bleacher Report's Matt Miller wrote of Hockenson. "His all-around game is so developed that he has the tools to start his rookie season with All-Pro traits."

There are also uncanny physical similarities between Ertz and Hockenson. Both are 6'5". Ertz weighed in at 249 pounds at the combine—two pounds lighter than Hockenson—and ran a 4.76 40-yard dash. Hockenson's 40 clocked in at 4.7 seconds.

At least a few teams will likely value Hockenson as a top receiver more than a tight end, because that's the type of rookie impact he can provide. While he is a similar player to Ertz, his receiving production in year one may be closer to that of Falcons wideout Calvin Ridley (821 yards, 10 TDs).

6. Ed Oliver, DL, Houston

Player Comp: Aaron Donald

It isn't fair to compare any potential draftee to Los Angeles Rams star Aaron Donald. The guy is a two-time Defensive Player of the Year and a four-time All-Pro. However, Houston's Ed Oliver—as a prospect—is close.

Like Donald, Oliver heads to the NFL with atypical size. Donald was 6'1", 285 pounds, while Oliver is 6'2", 287 pounds. Both are between the archetypal sizes for interior defensive linemen and defensive ends. Donald has shown, however, that looking the part isn't as important as playing it.

Also like Donald, Oliver is incredibly athletic. He ran a 4.19-second short shuttle at his pro day, which is even faster than the 4.39-second shuttle Donald ran at the combine.

Is it a long shot that Oliver is the next Donald? Sure, but it's not unrealistic to view this as his ceiling.

7. Josh Jacobs, RB, Alabama

Player Comp: Sony Michel

At some point during the draft process, you're likely to hear Alabama's Josh Jacobs compared to New Orleans Saints running back Alvin Kamara. However, this has more to do with Jacobs' limited workload at Alabama than his skill set.

Kamara had just 210 carries in the 2015 and 2016 seasons combined for the Tennessee Volunteers. Jacobs had 166 over the last two years. He should have fresh legs, as Kamara did coming out of college, but they are different types of players.

Expect Jacobs to be more like New England Patriots back Sony Michel than Kamara. While the 5'10", 220-pound Jacobs does have some wiggle in his running style, he's more of a power runner. He can be a three-down pro back, but he isn't likely to serve as an extra receiver the way Kamara often does.

Jacobs should be a bit more involved in the passing game than the 5'11", 215-pound Michel was as a rookie (just seven receptions), but he should have a similar impact on a team's rushing attack. Michel produced 931 yards and 4.5 yards per carry. That's a realistic rookie goal for Jacobs.

8. Jonah Williams, OT, Alabama

Player Comp: Cameron Erving

Because of his arm length (33⅝"), some teams may view Alabama's Jonah Williams as an interior lineman instead of an offensive tackle. This is what happened to 2015 first-round pick Cameron Erving (34⅛" arms), who played left tackle at Florida State but has settled in at guard for the Kansas City Chiefs.

Now, Williams is a more polished technician than Erving was as a prospect, but his ability to overpower defenders at the point of attack is similar.

"Draft him, put him at OT or OG, he will block the player in front of him," former NFL lineman Geoff Schwartz tweeted of Williams. "That's what matters."

The fact that Erving didn't pan out with the Cleveland Browns shouldn't make this a scary comparison. He's become a terrific fit for the Chiefs, as he's a reliable starter at guard who can fill in at tackle if needed.

9. Jeffery Simmons, DL, Mississippi State

Player Comp: Ndamukong Suh

If we're examining skill sets and frames, Mississippi State's Jeffery Simmons compares favorably to 6'4", 313-pound star Ndamukong Suh. He's big (6'4", 301 lbs), powerful, disruptive and capable of impacting opposing offenses almost entirely by himself.

"Simmons isn't quite as jaw-droppingly strong," Chris Trapasso of CBSSports.com wrote. "He's in the Suh realm though. He physically overpowered most SEC offensive linemen he faced. His arms generate a ridiculous amount of power, and he can counter off his bull rush very well."

The caveat with Simmons is that he suffered a torn ACL while preparing for the scouting combine. He'll make a major impact on some NFL defense, but it might not happen until his second year.

10. Rashan Gary, EDGE, Michigan

Player Comp: Trey Flowers

While Michigan's Rashan Gary is more of an all-around defensive end than a pure edge-rusher, that isn't necessarily a bad thing. As Trey Flowers proved during his time with the New England Patriots, the ability to set the edge, pressure the quarterback and attack ball-carriers at the line out of a multifaceted role is valuable.

Interestingly, Bleacher Report's Matt Miller put Gary on the Detroit Lions—who signed Flowers in March—in a recent mock draft. This isn't too surprising, as the two have similar skill sets and could be used interchangeably in the Detroit defense. 

"The beauty of this selection is that the Lions can play Gary inside or outside, depending on the down-and-distance," Miller wrote. "He worked at defensive end and defensive tackle for the Wolverines and, at 277 pounds, he has the size and athleticism to thrive in either situation."    

11. Devin Bush, LB, Michigan

Player Comp: D'Qwell Jackson

D'Qwell Jackson hasn't played since the 2016 season with the Indianapolis Colts, but if you remember him, you'll remember an undersized (6'0", 242 lbs) stat-racker who thrived at inside linebacker. Despite missing all of the 2010 season with a torn pectoral muscle, Jackson still averaged more than 100 tackles per season in his 11-year career.

This is exactly the type of player Michigan's Devin Bush can be. The 5'11", 234-pound prospect can let blockers overwhelm him—just as Jackson did at times—but he has the speed and instincts to flow to the football and cover in space. Last season, he amassed 66 tackles, 8.5 tackles for a loss and 4.5 sacks.

Whichever team adds Bush will get a true sideline-to-sideline defender and a leader in the middle of the linebacking corps.

12. Montez Sweat, EDGE, Mississippi State

Player Comp: Ezekiel Ansah

Mississippi State's Montez Sweat leaped into the draft spotlight with an impressive Senior Bowl week and an even more impressive combine outing. He ran a ridiculous 4.41-second 40 in Indianapolis to go with a 125-inch broad jump and 36-inch vertical.

Sweat is more than just a workout warrior, though. While he is a bit raw, his long, flexible frame (6'6", 260 lbs) gives him a lot of bend on the edge, allowing him to push past blockers despite an unrefined arsenal of rush moves.

Sweat's 12 sacks in 2018 didn't come by accident.

Ezekiel Ansah was a similar prospect in 2013 out of BYU. A rangy, raw rusher then, Ansah proved early (15.5 sacks in first two seasons) that his skill set translated to the NFL. Sweat can have a similar impact early in his career.