Ames, Iowa ? Iowa State’s struggling offensive line has taken another hit.

Offensive center Mike Knapp had surgery on his right knee Monday and is lost for the rest of the season, and tackle Ben Lamaak is day to day because of a leg injury, coach Gene Chizik said Monday.

Knapp has been the Cyclones’ hard-luck player. A former walk-on, he started the first three games, then had his appendix removed on Sept. 16. Knapp returned to the starting lineup in last Saturday night’s 49-35 loss to Texas A&M after missing four games, but injured his knee on the sixth play.

He has a torn patellar tendon, which connects the kneecap to the shin bone.

“Mike’s had a tough go this season,” quarterback Austen Arnaud said. “I talked to him at halftime and he was just down. It really stinks because he’s a great kid.”

Knapp, a 6-foot-3, 272-pound junior, joined the Cyclones without a scholarship in 2005 after playing at West Des Moines Valley High School. He redshirted that first year and barely played in 2006 and 2007.

Chizik put him on scholarship this past summer and he earned the starting job, only to be dealt a double whammy of setbacks.

“My heart goes out to him and his family,” Chizik said. “When you sit there and watch Mom and Dad and sister and girlfriend and everybody crying after the game, how can your heart not go out?

“It’s really hard for him and his family. It hurts our football team, too, but that’s not the main issue. The main issue is him and his family and the struggle they’re going through right now.”

Chizik said he’s confident Knapp can get through it and return next season. Still, Arnaud said it’s hard when he sees a teammate go down.

“He’s undersized. He works his butt off,” Arnaud said. “He’s only 275 pounds playing center in the Big 12. Pound for pound he’s definitely one of the strongest guys on our football team. I think he’s the strongest guy on the offensive line. It’s just sad to see him not be able to play.”

Lamaak also went out early in the A&M game and did not return. Chizik didn’t disclose the nature of Lamaak’s injury, but it’s not believed to be serious. Arnaud, who rooms with Lamaak, said the 6-5, 315-pound sophomore was “walking around the house dragging his leg” on Sunday.

“I think those are the kind of things at this point in the year that pop up,” said Chizik, whose team plays at No. 9 Oklahoma State next Saturday.

“It’s everywhere on our team with guys getting nicked and dinged up. That’s what happens when you’re going into game nine.”