INDIANAPOLIS – Today marks the official end of training camp with the Detroit Lions competing in their preseason finale this afternoon against the Colts.

It's one last opportunity for players on the roster bubble to make a good impression before the team must trim the roster to an initial 53 by Sunday's 6 p.m. deadline.

"A lot of competition, a lot of good players. And we're going to have to let go of some guys that are going to be able to go to other rosters and make some waves," Lions head coach Dan Campbell said this week. "That could happen. That's real and that's hard to do. But yeah, this is going to be hard, man, on Sunday."

Here are five things I'll be watching out for in today's preseason finale:

1. TOUGH D-LINE DECISIONS

This Lions' defensive front has been impressive in camp and there's a lot of expectations for the collective group heading into the regular season. Before we get there, there's some tough decisions that will have to be made for the final couple spots upfront on defense.

"It's interesting, the D-line room is the most interesting," Campbell said. "It's just top to bottom, there's a ton of good players in there, we feel like."

After Aidan Hutchinson, DJ Wonnum and Derrick Moore, who gets one of the last edge spots? Ahmed Hassanein, Eric O'Neill and Anthony Lucas have all shown promise and playmaking ability in training camp practices and the preseason. A big performance today by one of these players could potentially push them into a roster spot. Or will one of the interior players who can play the big end spot make up one of those edge spots?

Coming to a decision on how to roster the interior of the defensive front might be even more difficult for Campbell and general manager Brad Holmes. Alim McNeill, Tyleik Williams and Tyler Lacy have taken most of the first-team reps. The depth after those three has has been fluid throughout camp. Levi Onwuzurike, Chris Smith and Mekhi Wingo are trusted veterans. Onwuzurike can also play the big end role. Rookie Skyler Gill-Howard and veteran Ben Stille have flashed in camp.

However the numbers ultimately fall in place, this is expected to be a talented, deep and versatile group that garnered a lot of praise from Campbell throughout camp with the way they've performed.

2. BACKUP QUARTERBACK

Will it be the veteran Josh Dobbs or undrafted rookie Luke Altmyer? Or will the Lions also consider a post-cuts addition to the quarterback room not currently in the building?

There's a lot on the line today for Dobbs and Altmyer as they try to make one last case for being Jared Goff’s backup this season.

In two preseason games so far, Altmyer has completed 22-of-35 passes (62.9 percent) for 216 yards with one touchdown, two interceptions and a passer rating of 65.9. Dobbs has completed 11-of-20 passes (55.0), for 106 yards with no touchdowns and an interception with a 49.2 rating. Dobbs has also added 62 rushing yards, including a 50-yard touchdown run.

Who moves the football more efficiently? Who takes care of the ball better? Those are two keys to watch today from both quarterbacks.

3. FINAL RECEIVER SPOT(S)

Campbell has said this is the best receiver room the Lions have had in training camp in his tenure in Detroit. That's high praise for that room and a compliment to Holmes and the work he and his staff did stocking the room as well as to assistant head coach/wide receivers coach Scottie Montgomery.

The unfortunate knee injury suffered by Cedrick Wilson Jr. and subsequent release from injured reserve with an injury settlement does give others an opportunity as Wilson was very much in the mix for what could be one or two spots on the initial 53.

Amon-Ra St. Brown, Jameson Williams and Issac TeSlaa are the clear top three based on training camp reps. Greg Dortch was brought in to compete for Detroit's open punt return job and has history in offensive coordinator Drew Petzing's offense. If he's in, that leaves players like Tom Kennedy, Tay Martin, Dominic Lovett, Lucky Jackson, Tarik Black and Malik Cunningham fighting for one or maybe two spots.

Something to watch closely today regarding this competition is special teams. How many teams are they playing on and with what units? The final receiver spots need to contribute and excel on special teams.

4. NICKEL CORNER

This is one of the few starter jobs still up for grabs.

I use the term starter somewhat loosely as this could be a spot where we see multiple players contribute game-to-game and week-to-week based on matchups, situation or scheme. Rookie fifth-round pick Keith Abney II has earned his way into a lot of first-team reps the last couple weeks when defensive coordinator Kelvin Sheppard goes into nickel defense. He's tough, can cover and seems to be a good fit.

Veteran Roger McCreary has played a lot of football in this league (61 games) with 38 starts both on the outside and in the nickel. Unfortunately, free-agent acquisition Christian Izien won't play today as he's dealing with an undisclosed injury that could affect his availability to start the regular season.

We've also seen Ennis Rakestraw Jr. and Nick Whiteside take some nickel reps in training camp. It will be interesting to see how Campbell divvies up those reps this afternoon.

5. RUNNING BACKS

I think all Lions fans are excited to see what Jahmyr Gibbs can do in this offense as the clear top back in Detroit with a heavy workload. Obviously, we'll have to wait a couple weeks for the regular opener vs. New Orleans for that.

In the meantime, there's a handful of backs we'll see against the Colts who have their eye on what might just be one roster spot at the position after Gibbs, Isiah Pacheco and Sione Vaki.

Jacob Saylors looks to have a slight edge as he's led the team in rushing in the preseason with 87 yards on 14 attempts for a 6.2-yard average. He's also been one of the top two kickoff returners consistently through camp after having that role for Detroit in the regular season last year.

Jobs have been won and lost in the preseason finale in previous seasons, and Jabari Small, Trayveon Williams and Roydell Williams will get an opportunity this afternoon to state their case for inclusion.