NASHVILLE, Tenn. -- Titans offensive coordinator Mike Heimerdinger left the team Wednesday and will undergo chemotherapy after a cancer diagnosis, coach Jeff Fisher said after practice.

The 58-year-old coordinator had not been feeling well for several weeks, but the team was taken aback by the development. Fisher declined to offer any further details.

"Mike is very sick," Fisher said. "And Mike is going to be, potentially as early as today, undergoing chemotherapy for cancer treatment. I don't know whether or not he'll be back [Thursday] or whether he'll be here inside the facility or whether or not he'll be able to participate in coaching this game."

The Titans were informed of the news just before practice, offensive lineman Jake Scott said.

The Titans concluded practice with a team prayer led by linebacker David Thornton.

"I'm not really good at saying or talking about things like that so thoughts and prayers go out to his family," receiver Randy Moss said. "Hopefully, his chemo and everything goes good, and we see him back as soon as he's ready."

Fisher said first-year quarterback coach Dowell Loggains and offensive line coach Mike Munchak will have input into the passing and running games, respectively. Loggains will likely call the plays while Fisher will maintain a close oversight, he said.

"We are going to continue with the game plan," Fisher said. "I will make sure this game will get called and the offense will be prepared. I just want everybody to keep Mike and his family in their prayers."

Rookie quarterback Rusty Smith will make his first career start with Vince Young (thumb) on injured reserve, Kerry Collins (calf) still healing and Chris Simms just re-signed.

"It's life, you know," Fisher said. "We have to deal with it and we have to move on. Not that we're moving on from Mike. Mike's on my heart; he's been on my heart for weeks. What he's done over the last couple weeks, considering how he's felt, is absolutely remarkable. I mean, it's remarkable. Then you add the events of the weekend to that and it doesn't make sense.