Purdue is in an interesting position.
They finally know who the starting QB will be going into the season. This is big because it was always 2 QBs splitting reps with the 1's going into opening week. This year O'Connell gets all the reps and can develop better timing with the WR's. O'Connell was the 2nd highest rated passer in the B1G last year, and I expect no different this year. He is by far the best QB in the B1G W, and better than every other QB in the B1G, aside from Stroud and Tagovailoa. I bet O'Connell puts up big numbers this year.
The OL has improved a lot over the years. They are finally coming around to having depth as well. Being able to protect O'Connell will give opposing defenses fits all season.
WR's will be interesting. Purdue recruits and develops this position extremely well. However, they just lost their clear #1 going into the season in Milton Wright (academically ineligible). Wright would have certainly been playing in the NFL (Purdue's 3rd drafted WR in 3 seasons). They have plenty of guys that can step up, problem is that the next 3 in line have been having problems with injuries. The Boilers did pick up a playmaker transfer from Iowa with Tracy.
RB lost starter Zander Horvath to the NFL. It's going to be tough to replace a guy like him as Purdue asks their RBs to do everything...pass block, run, and be a WR. King Doerue has a lot of experience, but struggled in pass block. Samson James is finally eligible and is expected to take a lot of snaps (former Ohio State recruit, and transfer from Indiana).
TE is an absolutely loaded position. No issues here whatsoever.
The defense was excellent last season, by Purdue standards. They could be counted on to win games. Problem is Purdue lost a lot of production.
DC Brad Lambert left, as expected. Purdue will now have their 4th DC in 4 seasons. We need continuity here. Hard to tell how English will run the show.
Karlaftis was a first round draft pick and his production will be hard to duplicate right away. Purdue does have some young 4* guys that could step up. They also got a big transfer in 4* Cole Brevard from Penn State.
The Boilers unexpectedly lost starting safety, and probably their best DB, Marvin Grant to transfer.
Special teams could get a big boost if Iowa transfer, and the B1Gs best return specialist, Charlie Jones picks Purdue.
So in short, offense should be very productive, defense is a question mark. Special teams could get a big boost.