Chris Houston started feeling tightness in his right foot early in last week’s 24-21 loss to the Tampa Bay Buccaneers, but the Detroit Lions cornerback didn’t give in to the pain until after he allowed Tiquan Underwood’s 85-yard touchdown catch on the second play of the fourth quarter.

Houston limped to the bench after that play, and he underwent an MRI on Monday that he was still waiting to hear the results of today.

“I don’t know (what the diagnosis is),” Houston said as walked through the locker room, leaving a protective boot by his locker. “I’m fitting to go have the doctor see right now.”

Houston said he doesn’t fear he has a stress fracture, but that the injury is “much more than” tightness.

If he can’t play Thursday against the Green Bay Packers, rookie Darius Slay will start in his place.

Houston said Underwood’s go-ahead touchdown was his fault and that he wasn’t expecting help from safety Louis Delmas on the play.

“Just kind of coming out of my break, I didn’t get out of my break good enough and wasn’t able to chase him down,” Houston said. “Didn’t have the speed to chase him down. Can’t just blame it all on my foot cause I ain’t the one to blame it on injuries, but didn’t come out of my break good enough.”

Wide receiver Calvin Johnson (knee) and linebacker Travis Lewis joined Houston on the sidelines at practice today, but Johnson said his knee is “getting better” and that he doesn’t anticipate it being an issue on short rest Thursday.