The Seahawks left themselves light at defensive tackle when they cut down to 53 players, choosing instead to keep 10 offensive linemen and J.D. McKissic.

It almost came back to bite them Sunday vs. San Francisco, as Carlos Hyde ripped off two big runs as he became the first back to go over 100 rushing yards twice against Pete Carroll’s defense in Seattle. So Carroll decided to beef up the middle again, calling up Garrison Smith from the practice squad to replace David Bass.

It’s the first of what could be two or three moves in the trenches this week.

Bass was beaten at the point of attack on Hyde’s 61-yard run that set up the 49ers’ first field goal. Of course, K.J. Wright and Kam Chancellor also misplayed it, but that probably was the play that made Carroll decide to add a fourth defensive tackle to support Sheldon Richardson, Jarran Reed and Naz Jones.

Carroll called the 61-yard play “a real big mistake on our part. We rarely hit plays like that where we didn’t fall back the way we needed to and we didn’t see it the way we needed to and all that. It was good execution by them and then we got into a big chase.”

The Seahawks decided to swap out defensive linemen rather than add to their numbers there, so they still have just eight guys.

They replaced Smith on the P-squad with a familiar face: Tyvis Powell.

Meanwhile, the Seahawks still have 10 O-linemen because they like left tackle Isaiah Battle, acquired from Kansas City amid the roster shuffling to 53. Battle is still learning Seattle’s system and seems unlikely to be active any time soon.

“Really like him, really like what he’s doing,” Carroll said. “He’s got an unusually gifted style of pass protection and we’re trying to catch him up with the system right now so that he can compete to play. He’s done some really good stuff; he’s going against our best guys in practice in pass rush and things like that, and he’s been very competitive. We’re really excited about it and what’s coming. I don’t know how fast we can get him caught up, but he’s done well.”

While Battle is just learning, others are battling to start. Oday Aboushi was inactive alongside Battle for Week 2, but he very well could replace a struggling Mark Glowinski at right guard this week.

“Oday’s done a really good job, (Ethan) Pocic’s done a really good job, Matt Tobin’s showing us that he can play too, so there are some guys that are available,” Carroll said. “It’s hard to get very many guys on game day up with the numbers and all of that, but the competition is on. … We’re looking to make sure that we keep it at the right edge to get better. We have to keep improving.”