The best part of Ben Roethlisberger's game has always been his deep-passing ability, but he has struggled in that area this season. (Joe Sargent/Getty Images)

All it takes is one look at the standings to tell you that the Pittsburgh Steelers are in trouble. They’re already two games back of the Bengals and Ravens in the win column in the AFC North — the latter of which they lost to in embarrassing fashion over the weekend, 26-14. They are tied for last place in the division with the Browns at 1-2-1 — and even Cleveland fans have more reason for optimism, given the hot start of rookie No. 1 overall pick Baker Mayfield.

Pro Football Focus

But a deeper look into the team’s performance through four weeks reveals the type of serious issues that not only suggest the Steelers are in danger of missing the playoffs, but that it’s actually a likelihood at this point. Using the help of Pro Football Focus grades and statistics, here are the five biggest reasons Pittsburgh could be shut out of the postseason.

Even if Le’Veon Bell returns, he can’t fix the offensive line.

Much of the discussion about Pittsburgh’s struggles has been centered around the absence of Bell, who is reportedly eyeing a return from his contract holdout in Weeks 7 or 8.

But that has overshadowed an important issue related to the team’s running game and overall efficiency on offense. One of the keys to the Steelers' sustained success in recent seasons has been the fact that they have had the same starting five offensive linemen since the end of the 2015 season, with only minor injury exceptions. It was a unit that could absolutely overpower their opposition when on top of its game, such as when allowing only two pressures on 32 dropbacks in a 2016 playoff win over the Chiefs.

Through four weeks of the season, that dominance has waned. As a team, they currently rank 25th in run-blocking grades and 11th in pass protection after finishing seventh and first, respectively, in 2017. With three starters — left tackle Alejandro Villanueva, left guard Ramon Foster and right tackle Marcus Gilbert — on the wrong side of 30, it’s worth questioning if their best days are behind them. They’re still a solid unit, but a far cry from the one of recent seasons. Bell’s return alone won’t fix Pittsburgh’s running game.

Ben Roethlisberger’s play appears to be on the decline.

We should preface this by mentioning that Roethlisberger has never been on the level of Drew Brees or Aaron Rodgers in terms of his accuracy. He’s been most successful by consistently finding favorable opportunities and making special throws down the field. Last season on throws 10 or more yards down the field, Roethlisberger had a 91.8 PFF grade (on a 0 to 100 scale) with a 54.1 adjusted completion percentage and 97.3 passer rating. This season, that’s dropped to a 63.5 passing grade, 42.9 adjusted completion percentage and 77.3 passer rating.

This is a far cry from the Roethlisberger we’ve come to know. His lowest grade on such throws in the past five years has only been an 89.0. The deep passing game is where he dominates, yet his touch seemingly has been lost. No player has been affected more than No. 1 receiver Antonio Brown. Over the past five seasons, he has hauled in 69.4 percent of the passes thrown to him. This year, that number is only 55.8 percent. Not every quarterback ages the same, and at 36 years of age, Roethlisberger’s play looks to be on the decline.

The defense really misses Ryan Shazier.

It’s difficult to overstate how much Shazier, who suffered a serious spinal injury last season, had meant to this defense. Losing an athletic linebacker such as Shazier is always going to be a huge blow, but his absence has been even more significant for Pittsburgh because of its coverage schemes. The Steelers have played the third-most snaps in Cover-2 (man and zone combined) of any team in the NFL. While those coverages can help hide some deficiencies at cornerback and limit big plays, it does so by asking the linebackers to cover more ground than any other coverage type.

Last season, in 11 games, Shazier had eight forced incompletions to go along with three interceptions. This season, the Steelers' off-ball linebackers have forced one lone incompletion and picked off zero passes. Jon Bostic and Vince Williams simply aren’t talented enough to make teams afraid of continually attacking over the middle of the field against the Steelers' zone coverage.

There is a lack of depth in the secondary.

The year is 2018, and it’s about time we started looking at a team’s third cornerback as a starter. They play as many, if not more, snaps than a lot of starting defensive tackles. Last season, Steelers nickelback Mike Hilton played 577 snaps, while nose tackle Javon Hargrave played 455.

It’s not simply enough to have one or two good cornerbacks, and after No. 1 corner Joe Haden, Pittsburgh’s have been awful. Artie Burns, Hilton, Coty Sensabaugh and Cameron Sutton have allowed 672 yards and seven touchdowns while recording just two interceptions, good for a passer rating of 135.4 (out of a possible 158.3).

That’s not going to get the job done, and there is little reason to think things will change anytime soon. Burns, the former first-round pick, has never had a coverage grade higher than 73.6 in his first two years.

They still don’t have a disruptive edge rusher.

The lack of high-level pass rushers isn’t a new issue, but it was thought to have been fixed by the selection of first-round picks in Bud Dupree and T.J. Watt, who are in their fourth and second NFL seasons, respectively. That hasn’t been the case, as Dupree has a lackluster 66.1 pass-rushing grade and Watt has recorded an even more disappointing 61.5. Given the issues at linebacker and cornerback, the Steelers simply aren’t going to be able to slow opposing passing attacks without a more disruptive pass rush.

More NFL coverage:

That time Patrick Mahomes and Baker Mayfield had the craziest college QB duel ever

The Bears believe in Mitchell Trubisky, and they might not be alone anymore

Aaron Rodgers delivers veiled criticism of the Packers' play-calling ‘plan’