Detroit's injury depleted secondary got a much-needed boost Wednesday when CB Chris Houston participated in individual drills for the first time since suffering a high-ankle sprain during the Lions' third preseason game.

Houston’s return to practice confirmed his assertions that he wants to be ready to make his 2012 regular-season debut when the Lions face the 49ers Sunday night. "I'm pushing as hard as I can," he said Monday. "I don't want to miss any games, because I know I'm a big piece to the back end.”

The timing of Houston’s return to drills couldn’t be better for the Lions’ injury-depleted secondary. Rookie cornerback Bill Bentley (concussion) didn’t participate in open drill periods Wednesday, and his status for Sunday’s game is uncertain. If Houston is able to play Sunday, it will give the Lions four healthy CBs with NFL experience -- a must against the 49ers’ talented offense.

WR Calvin Johnson (undisclosed) and S Louis Delmas (knee) also missed Wednesday’s individual drill periods. Delmas hasn’t practiced since he underwent surgery on his knee during training camp, so his absence won’t affect Detroit’s Week 2 plans. Johnson is one of the hardest workers on the Lions’ roster, so it’s noticeable any time he misses a workout. Jim Schwartz will often rest key veterans on Wednesdays, so there’s no cause for concern unless Johnson misses Thursday’s workout.

Follow Lions reporter John Kreger on Twitter at @CBSLions and @JohnKreger.