I accidentally put a player on IR in preseason but now I can see him on the depth chart.
Is this a bug?

I think he’s deactivated though. The logic will just skip that spot and search for the next guy on the depth.

...speaking of legacy bugs, the use of IR in MFN is not and never has been according to NFL rules. Not since I joined September 2018.
Yet another item I "thought" would be addressed in 4.6 that just...
Wasn't.
Ditto for 4.5. Ditto for 4.4....

I would have been happier if 4.6 was ONLY a rules/roster/interface update and nothing else.
Catching MyFootballNow up to the current RL NFL rulebook would have simply been enough. It really would have.

Some of us already did 4.4 (<- mumbled grumbling of yaddas).
Please, dear Zod, permit 4.7 to be the update that fully brings MFN up to date with whatever current RL NFL rules and roster requirements are in place at such time of release of the next MFN update.

Ya wouldn't be worried in the first place about a pre-season IR mistake if the actual NFL IR rules were used in MFN.
^^^^^^^^
THIS.

I should add that when cleaning up a team's roster, being able to place a burdening cap player on IR early is such a YUGE bonus roster and cap wise for that season. One of my favourite cap abuses in a rebuild when it presents. Free cheapie with a 2 yr contract I won't mind cutting and will love keeping.
54 players ;)