The regular season is half over for Ohio State, yet it feels as if the Buckeyes are just finding themselves.

The 12th-ranked Buckeyes (5-1, 2-0 Big Ten) have inched their way up the rankings a bit since that ugly 35-3 loss at Southern California in mid-September.

‘‘We can’t lose,’’ fullback Brandon Smith said Tuesday. ‘‘We’ve been saying this is a playoff for us, at this point in the season. The way things shake out in college football, we’ve just got to keep winning.’’

Since the loss, the Buckeyes have won three in a row, including their first two Big Ten games. They’ve gotten Chris ‘‘Beanie’’ Wells back from a foot injury, and freshman Terrelle Pryor has taken over at quarterback. Even though they have not won convincingly, they at least believe they’re building some momentum for a stretch run.

Punter A.J. Trapasso considers last Saturday night’s 20-17 victory at Wisconsin a stepping stone to bigger and better things.

‘‘We had a lot of confidence coming into this season, maybe (we were) a little bit overconfident thinking we were just going to run over teams,’’ Trapasso said. ‘‘We were exposed a little bit (at USC) but we’ve bounced back pretty well, and handled some rough games — especially this (past) weekend.’’

Going into the season, the Buckeyes had 17 starters back and more than 40 fourth- or fifth-year seniors on the roster. No one expected much upheaval from one week to the next.

Instead, there has been almost continual change.

Two or three fresh faces have been blended in on the offensive line, three backs filled in for Wells at tailback while he was sidelined, and the defense does not have set starters on the line or at one of the cornerback spots. Nothing was more radical than changing from second-year starter Todd Boeckman, a big pocket passer, to Pryor, a 6-foot-6 sprinter.

So rather than fine-tuning, the Buckeyes have been revamping. It may take quite a while longer until things settle down.

‘‘I would attribute some of that to just figuring out our offense, getting people used to playing new positions and trying different things,’’ Trapasso said. ‘‘We went into the season with the mind-set of doing one thing offensively and now we’re midway through and we’re doing something that seems to me completely different.’’

The Buckeyes are adapting. They’re also growing in confidence.

‘‘We are moving in the right direction at this point,’’ Smith said.

This week’s challenge will be provided by Purdue (2-3, 0-1), which has lost three of its last four while giving up lots of yards and not showing much consistency on offense.

But the Boilermakers present a change of pace from Wisconsin. Where the Badgers ran the ball right at the Buckeyes and didn’t stretch the field much, Purdue is the epitome of a spread offense.

Coach Jim Tressel repeatedly referred to the problem of ‘‘shifting gears.’’

‘‘We have to kind of get ready for a different mode,’’ he said.

Getting ready for a spread team after playing a traditional running team wears on the coaching staff, perhaps more so than the players. Like hitters facing a hard-throwing reliever after facing a knuckleballing starter, the Buckeyes need to prepare for the change of speed from what they saw at Camp Randall Stadium.