One quarterback couldn't get on the field, while the other had just been yanked from it.

The difference, though, was that Clark watched his team go down in flames without him, as Williams - despite the blow to his ego - watched his replacement coax his team to victory.

That was last season, as unranked Illinois upset a then-ranked Penn State, 27-20. This season, both quarterbacks are back, but this time Clark is starting, and Williams won't be looking over his shoulder.

When No. 12 Penn State (4-0) hosts No. 22 Illinois (2-1) in tonight's Big Ten opener, the opposing quarterbacks will likely have a more prominent say as the game winds to its conclusion.

Clark, a backup last year, could do nothing as Anthony Morelli threw three interceptions and fumbled - all deep in Illini territory - on the Lions' final four possessions.

"I wanted to play that game, period," Clark said last Saturday after the Lions pounded Temple, 45-3. "It wasn't, 'He's doing terrible. I need to be in.'

"Any time things are not going right, you feel: 'I could have done this. I could have done that.' That was last year. I have that chance this year."

Clark also has a chance to prove that his near-faultless run through the first four games - and his team's - was not just a product of playing inferior competition. For the season, the junior has thrown for 715 yards on 48 of 78 passing. He has tossed seven touchdowns against one interception and has run for two scores.

"We think they're a better football team than they were last year," Illinois coach Ron Zook said. "More importantly, we think the quarterback position is much improved over last year."

Zook didn't mention Clark by name, because he, too, has a capable backup. The difference being this year coach Joe Paterno hasn't been as shy about using Pat Devlin. Clark's the guy, but there's no reason to think that if he struggles, he won't suffer the same fate Illinois' Williams did last September.

Williams guided the Illini to a 24-20 lead through three-plus quarters, but failed to do much of anything for most of the second half. So Zook hooked him for Eddie McGee, who scurried 53 yards on his first series to set up a field goal and the game's final score.

Williams had his starting job back the following week and went on to lead Illinois to a Rose Bowl berth, but he was often inconsistent in doing so.

The 6-foot-2, 233-pound Williams is similarly sized to Clark (6-2, 235) and is a dual threat like his counterpart. But Williams is more apt to run (46 carries for 219 yards) and isn't as accurate a passer.

Arrelious Benn is Williams' top target. The sophomore wide receiver was instrumental in Illinois' win last season, returning a kick 90 yards for a touchdown and scoring when he shook four would-be tacklers on a 29-yard reception.

"I watch that play all the time on the Big Ten Network," Penn State linebacker Navorro Bowman said. "I went for the strip instead of the tackle."

Bowman was also on the field for Benn's kick return. Last season, the Lions' coverage was among the worst in the nation. The unit looked solid in the first three games this season but surrendered 36.8 yards per return to Temple.

Fumbles have also been a concern. Penn State has put the ball on the turf 11 times in the last three games, with only four resulting in turnovers.

But that is just nit-picking. The Lions have been sharp, which is why there is great anticipation for tonight's game. Hundreds of students have camped outside Beaver Stadium in the area known as "Paternoville," and thousands more are expected to take part in a stadium-wide "white out."

Of course, it may be difficult to find 110,000 white parkas. Forecasters are calling for a heavy dose of rain.

or jmclane@phillynews.com.