Tressel revealed that Krenzel threw Monday for the first time since suffering an elbow injury on his right throwing arm in the first half of the Sept. 13 game with N.C. State.
"Craig threw lightly yesterday," Tressel said. "We will find out what the trainers and doctors will let him do. I don't know if we'll find out before Thursday. We should know by the end of the day on Thursday whether he will play significantly, play sparingly or not be able to play at all."
Although some have speculated that OSU should hold Krenzel out against Northwestern (2-2), Tressel said the quarterback would likely play if deemed healthy by team medical personnel.
"It's up to the doctors," Tressel said. "If they say he will go, he'll go. If they say to me he can go, we're not going to be cautious. We're playing in the Big Ten. This is no time to be cautious. But if they say he shouldn't go, that's when you need to be cautious."
Tressel was asked if Krenzel reported pain after throwing on Monday.
"I did not see him after he threw yesterday," he said. "The trainers said he threw lightly and seemed to go fine. I think it would be typical with any kind of trauma to have some soreness. That pain and discomfort goes with it."
Tressel also updated injuries to several other players.
"Alex Stepanovich (ankle) looks better, but I would still call him questionable for Saturday," he said. "Darrion Scott (ankle) I would call doubtful. Adam Olds I would call probable. Branden Joe (torn pectoral) I would say is definite. He's been cleared to go."
The coach noted that autumn quarter classes begin Wednesday.
"We start classes tomorrow and that is exciting thing for some of the guys in their first year here," he said. "For the other guys, they need to keep progressing toward their degree. Some of our guys are anxious to get going. I think they do a better job of time management once class starts."
Saturday's game also begins the quest for a second consecutive Big Ten championship.
"We are starting Big Ten play," he said. "We all know whatever goes on in the preseason, the Big Ten teams play each other extraordinarily. You have to play four full quarters if you want a chance to be the Big Ten champions."
Tressel said it would be a mistake to discount Northwestern, which has been up-and-down so far this year.
"Last year at this time, if you look up to the games leading up to this, the teams they played were similar but the scores have been different," he said. "Air Force scored 50 points on them last year. This year, Northwestern should have beaten them. They were up 21-9 and lost a heartbreaker (22-21).
"They played against Duke last year and were fairly even. This year, they dominated the Duke game. There was no doubt who was the better team.
"We went there last year and had a battle for 60 minutes. The score was 27-16, but it was tighter than that. Northwestern did an extraordinary job on special teams with a long punt return and a long kick return.
"We know when you take the field in the Big Ten, you can forget about what you've seen on film."
Tressel was asked to assess the play of quarterback Scott McMullen, who replaced Krenzel against Bowling Green.
"Scott graded out just under 80 percent," he said. "We need our quarterback to grade about 85 percent for him to get a winning performance. He was pretty solid, but he had never played in a 67-play game since he's been here.
"There are a couple plays he wish he could have over. He did some good things and seemed to be in command of what we're trying to do. I think he gained some confidence. He looks like a guy who can contribute what we need at that position.
"But he did have two turnovers with an interception and a fumble. I don't know if you can have a winning performance with two turnovers like that."
Tressel has faith in McMullen if he is needed to pilot the ship for the long haul.
"Scott knows what we've talked about for years and years here at Ohio State and what it takes to win," he said. "He understands what his contribution needs to be.
"I think he's a role model as a fifth-year senior, playing at Ohio State in the shadows. He got his opportunity to start at quarterback for Ohio State. I think the message is if you hang in there, your day will come."
The Players Speak
Tressel was joined at the luncheon by three Dayton-area standouts -- center Nick Mangold, linebacker A.J. Hawk and kicker Mike Nugent.
Hawk said he enjoyed watching other college games -- particularly Michigan-Oregon and Iowa-Arizona State -- after the Buckeyes played Saturday.
"I actually watched all of the Michigan game when I got back to my place," he said. "Then, I watched Iowa. You get a little gist of what they do by watching them. It's relaxing to me to sit back and watch other teams play."
Mangold added, "I watched Michigan-Oregon back at my house. I had a lot of family and friends there. I don't watch it so much to scout other teams, but you can get an idea on what's going on with them."
Hawk was asked about Maurice Clarett's bid to sue the NFL to enter the draft a year early.
"We learn what we hear from you guys," Hawk said. "You guys are the ones who give us the information. If I knew the whole story, I'd maybe know more.
"We respect Maurice. We know he's probably just doing it to test the waters and see what's going on. Hopefully, he can get it all worked out and come back next year for us."
Hawk said he doesn't necessarily believe underclassmen should be able to go to the NFL before their third year in college.
"Football is different," he said. "I agree with the three-year rule. Football is a bit different than basketball. There are grown men in the NFL. Your body needs to grow and mature to handle that. I understand why they have the three-year rule."