The Bryan Harsin era has begun, and as one would imagine for a new coach replacing a fired predecessor, there’s no shortage of issues that need to be fixed.

Of primary concern will be improving a lackluster passing game that is losing its top 3 receivers from 2020. Bo Nix returns, but it remains to be seen whether he’ll remain the starting quarterback. Tank Bigsby returns, thank goodness. And though Auburn returns all of its starting offensive linemen, the group left a lot to be desired last year, and there are no real additions this offseason to inspire overnight improvements.

Derek Mason’s defense stands in better position, but between some crucial departures via transfer and to the NFL Draft, there will be a few pivotal positional battles.

Here’s a look at the 5 biggest holes Auburn needs to fill in 2021:

WR: Elijah Canion to replace Seth Williams

Auburn lost a lot of production from its receivers this offseason — like 67.1% of its receptions, 72.2% of its receiving yards and 83.3% of its touchdowns from last season. Williams, Anthony Schwartz and Eli Stove are all gone.

What the Tigers lack in experience, there’s no shortage of talent. Canion appeared in just 2 games last year, but he left a statement in the Citrus Bowl. The 6-4, 213-pound wideout caught 3 passes for 80 yards and a touchdown against Northwestern and has all the momentum he needs to develop this spring and quickly become Nix’s new No. 1 target.

S: Chris Thompson Jr. to replace Jamien Sherwood

Losing Sherwood to the NFL along with Jordyn Peters was certainly a big hit for an Auburn secondary that is otherwise well-equipped to improve off 2020’s performance. Thompson played the most of any young DB last year for the Tigers and should have the early lead to start alongside Smoke Monday in Week 1.

With that being said, Auburn loaded up on safeties in its 2021 recruiting class, including 4-star prospect Ahmari Harvey and 3-star prospects Cayden Bridges and Juwon Gaston. Harvey in particular will compete with Eric Reed Jr. to take that starting role from Thomspon by season’s end.

DE: Colby Wooden to replace Big Kat Bryant

Bryant followed Kevin Steele to Tennessee (although Steele is no longer employed by the Vols because, well, Tennessee) and opened up a big hole on the edge for Year 1 of Mason’s defense. Bryant finished 2020 with 17 tackles, 3 sacks and was a team captain, so his leadership will be a loss that Wooden likely won’t replace.

Wooden started 2020 on the interior before moving to the edge where he did the majority of damage. Wooden led the Tigers with 9.5 tackles for loss and had 3.5 sacks among his 41 total tackles. Who becomes Wooden’s counterpart on the other side will be an interesting battle between players like Zykeivous Walker and Northwestern transfer Eku Leota.

DT: Dre Butler to replace Daquan Newkirk

Auburn received good news this past week in the form of Tyrone Truesdell electing to use another year of eligibility, but the Tigers weren’t so fortunate with Newkirk, who transferred to Florida.

Left to replace Newkirk’s 10 starts and 28 tackles in 2020 will be a platoon of players, likely led by Butler. The JUCO transfer missed Auburn’s first 2 games but played a larger role in the defense with each passing week, finishing the year with 14 tackles and a sack.

WR: Shedrick Jackson to replace Anthony Schwartz

Back to that receiving group that was so decimated by offseason attrition, Nix is going to need more than one steady guy if he’s to keep his job all season. Hampered by an injury last season, Jackson played in just 6 games, but he’s Auburn’s most-experienced wide receiver.

Although he only had 6 catches for 84 yards last season, Jackson also is Auburn’s best blocking receiver, which may not be quite as important in 2021 if the Tigers move away from an offense that relies heavily on sweeps. Look for someone with more speed like Malcolm Johnson Jr. to emerge by season’s end.