I’ll admit I may have been overly optimistic about Tank Carradine in 2016 – much like I was about the entire 49ers’ roster.

Carradine would finally be used correctly, I thought, working as an edge rusher in passing situations now that he’s fully transitioned to outside linebacker. I even said – out loud, to multiple people – I thought Carradine could lead the 49ers in sacks after an impressive preseason.

With Ahmad Brooks on the wrong side of 30 and Aaron Lynch suspended for the first four games, Carradine seemed like the player the 49ers were counting on to break out. He might have been the reason Trent Baalke didn’t find an edge rusher in the recent draft.

But Carradine didn’t play a single snap on defense Sunday against the Buccaneers.

Here’s Chip Kelly’s explanation Monday:

“Just the rotation that those guys had going. I think they felt really comfortable with what Eli (Harold), Aaron’s (Lynch) reps were up a little bit coming back. I think he’s got a little bit more wind in him in terms of where we are. We felt (Ahmad Brooks) was playing really well. So, they tried to keep Aaron in the game as much as they can. So, it was just a rotation. And (outside linebackers coach Jason Tarver’s) in charge of those guys on game day in terms of the rotation that we’ve got going at the outside linebacker spot.”

Carradine’s apparent demotion is notable considering he signed a one-year extension before the season, indicating the 49ers were hoping they could get him cheaply for 2017 before a productive season inflated his value on the open market. An extra year of control meant San Francisco could sign him to a long-term extension before anyone else.

But Carradine’s struggled to set the edge in the running game. The 49ers have been miserable defending the run, particularly in sub packages, where Carradine got the bulk of his playing time.

There’s another angle to Carradine’s demotion Sunday – as pointed out to me by Matt Barrows of the Sacramento Bee: Maybe the 49ers are considering trading the second-round pick from 2013.

That would make a lot of sense. The trade deadline is Tuesday, Nov. 1 and Carradine would fit much better on a team that uses a base 4-3 defense that could support Carradine with an extra linebacker playing behind him.

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In the 49ers’ sub package, Carradine plays with only two linebackers on the field. In a base 4-3, he would have three, which could help cover up his run-disrupting deficiencies.

If San Francisco was angling to trade him – likely for a fifth or sixth-round pick – they’d like to keep him healthy. Plus, he has more value on the trade market given he has another year on his contract.

Carradine has never been a good scheme fit despite showing flashes of being able to get after the passer. If the 49ers aren’t playing him now, it’s hard to envision a long term future for Carradine in red and gold.