Donte Smith finds his way off the bench behind Mike Gerrity

Donte Smith used to be USC’s starting point guard.

Then Mike Gerrity came along, took the spot, stole everyone’s hearts, and now, with four straight wins, the team has gone from bottom dweller to possible contender in the Pacific 10 Conference.

For Smith, who started USC’s first eight games, Gerrity’s ascension means a new role: seldom-used reserve.

In the first eight games, Smith averaged 32.3 minutes, but in USC’s last four he’s averaged 7.3. He didn’t play at all in the Trojans’ last game, against Nevada Las Vegas in the championship game of the Diamond Head Classic, because of a wrist injury.

“It was frustrating at first, but I thought about it, and, hey, I’ve got to go with it -- we’re winning,” Smith said.

When Gerrity, who sat out after transferring from Charlotte, became eligible Dec. 18, USC Coach Kevin O’Neill started him the next day.

“Mike, obviously, is the right guy to be playing the point for us,” O’Neill said. “That’s proven out. Donte did as good of job as he could in the eight games Mike was out, and now he has to, and has found a way to, contribute off the bench.”

Like he did in USC’s 55-51 win against Western Michigan in the first round at Hawaii on Dec. 22. With USC trailing, 42-38, with 7 minutes 38 seconds left in the game, Smith scored six straight points to give USC the lead.

Smith and Gerrity get along well. Each acts as the other’s eyes.

“In Hawaii, every timeout he was coming up, slapping me on the back, encouraging me,” Gerrity said. “Whatever he could do, whatever he saw. He was telling me, ‘Hey take advantage of this, look for that.’ He’s just been the ultimate teammate.”

Swing man

Marcus Johnson is consistently inconsistent.

Every other game for the last eight, the senior forward has scored in double figures, then single digits. Some games he has filled up the stat sheet -- a few blocks, assists and steals here, quite a few rebounds there -- and some games he hasn’t.

Against Nevada Las Vegas on Friday, the senior forward had career highs with 19 points and nine rebounds. Johnson scored USC’s first six points and was solid throughout.

“When he has great energy, he plays great,” O’Neill said. “When his energy is so-so, he doesn’t play particularly well.”

Johnson, who is averaging 9.8 points and six rebounds, said he carries the same mind-set into each game: “Hit first, come out aggressive, make sure you’re ready.”

Why is Johnson off some nights?

“Every game is different,” he said. “Things happen differently. You never know how the ball is going to roll.”

baxter.holmes@latimes.com