Injured Johnson doesn’t practice

USC tailback Stafon Johnson did not practice Monday because of a kneecap injury, but the junior said he would play in the Rose Bowl against Penn State on Jan 1.

Johnson was hurt Sunday when he was hit after catching a pass. Johnson said it felt like something in his right knee “went out and then came back in,” but he was able to walk to the sideline and later to the locker room without assistance.

Coach Pete Carroll said X-rays revealed no major damage.

“At first I was very scared because I didn’t know what was going on,” said Johnson, who has a team-high 123 carries for 642 yards and nine touchdowns. “But no matter what it was, it wasn’t going to keep me out of the game.”

Johnson was dressed in sweats as the Trojans went through their final workout before a three-day holiday break.

The Trojans played a spirited mock game, first practicing special teams transitions before scrimmaging.

Reserves took most of the repetitions, with quarterback Garrett Green tossing two touchdown passes.

Not sentimental

Steve Sarkisian already has the job as Washington’s new head coach, but USC’s offensive coordinator acknowledged that he could continue to build his resume and head to Seattle on a high note if the offense plays well against Penn State.

“It can’t hurt, that’s for sure,” Sarkisian said. “We need to go win the game -- that’s the most important thing.”

Sarkisian is not getting misty as his tenure with the Trojans winds down. Sarkisian, the Oakland Raiders’ quarterbacks coach in 2004, has spent seven of the last eight years with the Trojans.

“I’m not that sentimental of a guy -- I’m pretty business oriented,” he said. “I’m going to try and enjoy these few days we have off and then it’s going to be a business-type attitude the last week .”

Sarkisian reiterated that his mind would be on the Trojans and not what awaits in Seattle.

“I really want us to go out and play well,” he said. “I’ll go up on [Jan. 3] and go to work.”

Quick kicks

Receiver Damian Williams (shoulder) was held out of practice to prevent him from negating progress made this week, Carroll said. Williams is expected to practice when the Trojans return and play in the Rose Bowl. . . . Fullback Stanley Havili (ankle) remained sidelined. His status for the Rose Bowl is uncertain.

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gary.klein@latimes.com