OSU then-redshirt sophomore quarterback J.T. Barrett (16) celebrates after a touchdown during a game against Michigan on Nov. 28 at Michigan Stadium in Ann Arbor, Michigan. OSU won 42-13. Credit: Samantha Hollingshead | Photo EditorThe window for underclassmen to declare for the NFL draft is officially closing Monday, which means the list of Ohio State football players departing the team for the next level is all but set in stone.And it is an expansive one.In all, 18 seniors, seven of which were starters, and nine underclassmen from the 2015 team will not be back in Columbus for another campaign.The result of this mass exodus of talent is gaping holes across coach Urban Meyer’s depth chart and, for fans, a lot of uncertainty surrounding the future of the team.Meyer is tasked with the onerous operation of filling the voids, which he will do throughout spring practice and fall camp. The first practices for next season aren’t until March 8, and the regular-season opener against Bowling Green is nearly eight months away, but questions about who will be on the field next year are present.In an attempt to provide answers to such questions, The Lantern is taking a look at which players are poised to replace the eight departed starters on each side of the ball, beginning Tuesday with the offense and concluding Wednesday with the defense. Pass catchers In Meyer’s spread offense, four pass catchers top the depth chart — two wide receivers, one H-back and a lone tight end.Michael Thomas, Jalin Marshall, Braxton Miller and Nick Vannett — the four players who occupied those spots last season — all will not be back in 2016, which translates into plenty of playing time for their replacements.The man likely leading the receiver corp in 2016 will be redshirt sophomore Noah Brown. Brown did not play a snap last season, but his name is one that was often talked about.The 6-foot-1, 240-pound New Jersey native was poised for a huge 2015 campaign, according to his coaches, but a broken leg days before the regular-season opener vitiated such plans. Back at full health, Brown should emerge as a trusty target for redshirt junior quarterback J.T. Barrett.At the second starting receiver spot, there is a bevy of potential contributors. It could be redshirt sophomore Parris Campbell, who predominantly saw the field on special teams last season but did play some receiver, or it could be redshirt freshman Torrance Gibson.Gibson, the five-star quarterback-turned-receiver, had a troublesome journey as a freshman and is really raw technique-wise, but he is an elite athlete with great measurables (6-foot-4, 205 pounds). If he has learned the position well enough after a year, he could make a splash. Beyond those three players, redshirt sophomore Terry McLaurin, junior James Clark and freshman Austin Mack could all fill in.Sliding in at tight end for the Buckeyes next year will be junior Marcus Baugh. Praised for his blocking in the run game, Baugh saw the field a decent amount this season. He will, likely, be a part of the passing attack more than Vannett was in 2015.As for who will replace Miller at H-back, that appears like it will be Dontre Wilson. The senior has been a contributor since first arriving in Columbus three seasons ago. He has dealt with injuries off-and-on during his career, but he has all the physical tools to regain his status as an offensive weapon.If Wilson isn’t the H-back, it will probably be junior Curtis Samuel, but Samuel’s more-likely role will be addressed later in the article. There is certainly talent within the pass catchers for next year’s team, but it is fair to say the best thing this group has going for it is that Barrett will be the one throwing the passes.Because of that, the aerial attack should be all right.Ground game The hole in the running game created by Ezekiel Elliott’s departure is massive. Of course, Barrett’s legs will be an asset on the ground for the offense, but he can’t run the ball every down.Who, then, will Barrett being handing the ball off to?It might be redshirt freshman Mike Weber, who battled injuries early in 2015 that set the stage for a redshirt season, but the second option — one that makes plenty of sense — is having Samuel return to backfield, where he played during the national championship run.With Elliott emerging as one of the nation’s premier running backs, Samuel may slide over to H-back in order to see the field with more frequency. A player with the game-breaking ability of Samuel needs to be touching the ball as much as possible, which is why putting him at H-back in 2015 made a lot of sense.But now, with Elliott out of the picture, starting Samuel at running back seems like the best option for Meyer. In two seasons, the Brooklyn, New York, product has accumulated 515 rushing yards on 75 carries. He has 33 catches for 384 yards, too.Samuel is versatile, with a propensity for explosive plays, and Meyer will want him to touch the ball as much as possible, which lends itself to the idea that No. 4 will return to the backfield in 2016.In the trenchesRegardless of who is trying to catch passes or run the ball, if the offensive line does not supply the needed protection in the trenches, it won’t matter.In order for that to happen, OSU will have to find a way to replace three starters along the O-line. Left tackle Taylor Decker, a probable first-round pick in the NFL draft, is gone, as well as center Jacoby Boren and right tackle Chase Farris.Fortunately for the Buckeyes, the two offensive lineman they do have returning are top-tier players. Redshirt junior left guard Billy Price and senior Pat Elflein are both set to be third-year starters.Elflein, who had previously been a right guard, is moving over to center, which is a huge boost for the offensive line, but that means both tackle spots and right guard are the positions that need replacements.Junior Jamarco Jones is pegged to take over for Decker at left tackle. It’s a tall task, no question, as Decker is one of the more well-respected O-linemen in OSU history, but Jones has the makings of a rock-solid replacement.The 6-foot-4 four-star recruit will have a lot of learning to do, but if he absorbed even half of Decker’s knowledge of the position, he should be a sturdy replacement.The other tackle spot will probably be occupied by sophomore Isaiah Prince. The 6-foot-7 Maryland native was a top 10 offensive tackle prospect and saw the field last season, albeit sporadically.Who will be next to Prince, however, is a little less clear. The top two candidates appear to be redshirt freshman Matthew Burrell and redshirt sophomore Demetrius Knox. The four-star recruits will spend spring practice and, potentially, fall camp battling it out for the offensive line’s final spot.The OSU offense finally got clicking in the final two games of 2015 and many of those key cogs will no longer be around. It would usually be safe to assume some drop off in performance when eight players depart, but Meyer is still at the helm and Barrett is back under center, so things might just be OK for the Scarlet and Gray.