San Francisco 49ers tight end George Kittle might be a mild-mannered and respectful citizen before NFL games begin, but he mutates into a scarlet-and-gold-clad superhero once game-day action begins. 

Kittle caught a team-leading nine passes for 83 yards during Monday's 27-23 loss to the New York Giants at Levi's Stadium. The setback doesn't take anything away from what the second-year tight end is doing without the team's starting quarterback, Jimmy Garoppolo, in the lineup. If anything, the key injuries suffered by the offense have allowed Kittle to become the focal point and fully realize his potential. 

The uber-athletic target with an affable personality should be wearing a cape based on his ability to carry the 49ers offense despite its limitations. 

"Kittle has been great," head coach Kyle Shanahan told reporters last month. "He's got a good personality. He acts like a WWE wrestler and I don't think that's an act; I think that's who he is 24/7, which is fun to watch. But you've always got to watch out for him. He's pretty rowdy all the time." 

Shanahan might not have known the half of it since his tight end has been fantastic for the offense's overall development despite the fact that the unit is down to its third-string quarterback. Kittle provides something a little extra. 

As Rob Gronkowski's star loses some of its shine and other top tight ends fail to complete their skill sets, Kittle's ascension among the league's elite seems inevitable. One or two good games get people talking. Seven out of 10 games with at least four receptions and 70 yards from the tight end position, including a pair of 100-plus-yard efforts, show that he's a consistent mismatch defenses are struggling to handle. 

But Kittle is very different from the league's best at his position. 

Gronkowski is a hulking figure at 6'6" and 268 pounds. When healthy, he can't be stopped. Therein lies the rub: The New England Patriots tight end is far from an iron man. In fact, the four-time All-Pro performer has already missed three games this season and is dealing with an ailing back. His decline appears to be underway. 

What makes Gronk special is his ability to affect the game in multiple areas. He is dominant as a receiver and a blocker. That's rare in today's game. Travis Kelce isn't a beast at the point of attack. His value is derived almost entirely from his ability to swoop in like a vulture in the aerial attack to pick apart defenses for the Kansas City Chiefs.

The Philadelphia Eagles' Zach Ertz is similar to Kelce. Ertz leads all tight ends and ranks third overall with 75 receptions (only three catches behind the league leaders, Adam Thielen and Michael Thomas). More often than not, he's detached from the line of scrimmage and tends to work out of the slot. 

Kittle is more chameleon-like with his ability to adapt—which is surprising since he played in a near-identical offensive system to Shanahan's as a member of the Iowa Hawkeyes. His collegiate experience helped him understand his fundamental roles as a receiver and in-line blocker, but he's added elements to his game that weren't seen in his college tape. 

"I think Kittle's got a pretty good feel of everything," Shanahan said. "He's got the ability to be a good blocker and a good passer. The more work he gets at stuff, the more he reps, I think he's got a chance to be a very well-rounded tight end, as everyone's seeing. So, I don't think there's anything that George can't do and can't do at a high level if he's given the opportunity and can do it consistently."

All of the signs were present before Kittle fell to the 49ers in the fifth round of the 2017 draft.

First, though the production wasn't always there for the former Hawkeye, he led the team with 10 receiving touchdowns through the 2015 and '16 campaigns. His routes needed to be honed and more precise, but it was clear he could get open and become a vital target, especially near the red zone. 

Second, the 6'4", 250-pound tight end posted the highest SPARQ (speed, power, agility, reaction and quickness test) score among his 2017 classmates, according to Three Sigma Athlete's Zach Whitman. It's amazing Kittle fell to the draft's third day considering his athletic prowess. But this is the same class that featured three first-round tight ends in O.J. Howard, Evan Engram and David Njoku. 

And, again, Kittle actually blocked—which top tight end prospects tend not to do. 

"That's a good question because we didn't know either," Shanahan said when asked why Kittle fell to the fifth round, per NBC Sports Bay Area's Jennifer Lee Chan. "We thought he was going to go somewhere in the third or something like that, was our guess. One thing that, to me, looks like first-round talent, but we had a feeling he was going to fall just in the fact that he didn't do a lot in the passing game. 

"All we hear about is people talking about him as a run-blocker and things like that, which is one of the reasons we really liked him. But, the main reason was the pass game. He didn't get to show that a ton, which helped him, we thought, not get noticed in the first couple of rounds. But, we were very surprised he fell to the fifth."

The translation hasn't been lost. Kittle has ravaged defenses. He leads the 2017 class with 775 receiving yards this season. The 49ers team captain already led all tight ends in yards gained per route and yards after catch coming into Monday's contest, per NFL.com's Graham Barfield. The Giants didn't have an answer, either, through the first three quarters of play before the 49ers inexplicably went away from him in the final frame. 

One play best encapsulates where Kittle stands among the league's elite. Two weeks ago, he ran a simple slant, snagged the pass with his left hand and raced down the field like Quicksilver for a 71-yard gain:

Kittle initially took a jab step to the outside before cutting to the inside, and it's easy to tell the defender's Spidey-sense started to tingle because he was in trouble. In fact, Kittle recorded the second-fastest time of any tight end this season during the play and already had three of the six fastest runs leading into the last two weeks of play, according to NFL Next Gen Stats. 

Improved route running, sticky hands, top-end speed, elite athleticism and, of course, reliable blocking are all found in one package. This combination places Kittle within striking distance of Gronkowski and Kelce as the game's best tight end, and he has a chance to surpass both in the near future.

Brent Sobleski covers the NFL for Bleacher Report. Follow him on Twitter: @brentsobleski.