Over the past 18 seasons, the Las Vegas Raiders have only reached the playoffs once (the 2016 season). And that was two years before Jon Gruden began his second stint as head coach.

The Raiders have been competitive the past two seasons, going 7-9 and 8-8 in 2019 and 2020, respectively. Both years, they got off to impressive starts, but they couldn't finish strong and find their way into the postseason.

That's why this is an important offseason for Las Vegas, as it looks to make the necessary moves to push it over the edge and back to the playoffs. The Raiders already have some young talent, but they could also be in the market for some veterans to fill the holes on their roster and help them put together a strong 2021 season.

Here's a look at three of the biggest keys for Las Vegas having a successful offseason.

Either Re-Sign Agholor or Add Another Veteran WR

The Raiders already have several young receivers who should continue to get better in future seasons. That group includes Henry Ruggs III and Bryan Edwards, who were both rookies in 2020, as well as Hunter Renfrow, who will be entering his third NFL season. There's a lot of potential among that trio.

But Las Vegas' leading wide receiver wasn't any of those three in 2020. It was Nelson Agholor, who signed a one-year deal with the Raiders and went on to notch 48 receptions for 896 yards and eight touchdowns, surpassing expectations. But now, Agholor is heading back to free agency, and he'll likely want a bigger salary for 2021.

Will Las Vegas be willing to pay that to bring Agholor back? If it is, its receiving corps will likely be set for next season. But if Agholor signs elsewhere, the Raiders should look to free agency to add another wide receiver, perhaps somebody who is a low-risk, high-reward option, like Agholor was last offseason.

However, ESPN's John Clayton recently told 93.7 The Fan that Las Vegas is "very interested" in top free-agent receiver JuJu Smith-Schuster. If the Raiders can find a way to bring in Smith-Schuster, it would be a huge boost for their offense.

That may not end up happening, but it should add a veteran receiver to lead its current group of youngsters and give quarterback Derek Carr a reliable target to throw to.

Add More Talent to the Defensive Front

The Raiders defense had plenty of struggles last season, but one of their biggest weaknesses was putting pressure on opposing quarterbacks. They had only 21 sacks, which ranked 21st in the NFL, and they don't have many strong pass-rushers on their roster (although defensive end Clelin Ferrell, a 2019 first-round draft pick, has the potential to improve).

In 2021, Las Vegas defense will have a new leader in defensive coordinator Gus Bradley, who will be looking to lead the unit to better results. And if he's going to do that, it would be nice for him to have some strong pass-rushers to utilize when deciding to dial it up and send a blitz.

Some of the top edge-rushers in free agency include Shaquil Barrett, J.J. Watt, Leonard Williams and Bud Dupree. Those players are all likely to sign big deals, but if the Raiders can find a way to make it work, they should try to bring in one of those defensive standouts.

Another option could be Melvin Ingram III, who spent his first nine seasons with the Los Angeles Chargers. Bradley was the Chargers defensive coordinator from 2017-20, and the 31-year-old Ingram could come at a more affordable price after a down 2020 season (no sacks in seven games). But he may still provide the veteran boost that Las Vegas' defensive line could use.

The Raiders could also use their first-round draft pick (the No. 17 overall selection) on a pass-rusher, depending on how the board looks at that point. Regardless of how they do it, they need to bolster their defensive front if they hope to see better results on that side of the ball in 2021.

Bring In Players to Compete for Jobs in the Secondary

Jeff Heath is the Raiders' starting free safety, but their defense would likely improve by moving him to a reserve role. Johnathan Abram is the starting strong safety, but he's struggled a bit early in his NFL career after being selected in the first round of the 2019 NFL draft.

While Abram is likely to continue to start, Las Vegas could benefit from adding a safety or two this offseason. It needs to bring in at least one to start at free safety next to Abram, then potentially acquire a second who can battle with Abram for the job and provide competition prior to next season.

There are plenty of talented safeties on the free-agent market this offseason, including John Johnson, Marcus Maye, Malik Hooker, Keanu Neal, Justin Simmons and more. So it's reasonable to think that the Raiders could one of them and add a standout player to their secondary.

Las Vegas could also be in pursuit of a cornerback, as its current group would likely benefit from the addition of another quality player. According to The Athletic's Tashan Reed, there is mutual interest between the Raiders and veteran cornerback Richard Sherman, so perhaps that could be a fit.

Much like its defensive front, Las Vegas' offseason will be successful for its defense if it adds to the secondary, no matter if that's through free agency, trades or the draft. But after last year's defensive struggles, the Raiders have to address these various needs in order to improve.