SANTA CLARA, Calif. — J.T. O'Sullivan's NFL Europe experience was like that of most quarterbacks who have played in the league: No blocking. No pocket. No time to throw. Plenty of bumps and bruises.

O'Sullivan's passes, however, had a way of finding their target in the spring of 2007. He threw 15 touchdowns against seven interceptions for the Frankfurt Galaxy, had a league-best 103.1 passer rating and was named offensive co-MVP.

At least one NFL evaluator took notice.

When Mike Martz, then Detroit's offensive coordinator, was given a tape of O'Sullivan that summer, he was reminded of one of his former pupils, Marc Bulger. O'Sullivan showed a knack for sidestepping the pass rush just long enough to get away the throw and even with such ferocious pressure, his passes were on target.

"I was looking for a guy who could make throws under duress and hard circumstances," Martz said. "It was obvious to me that he was very accurate and very intelligent."

Of the six free agents the 49ers added earlier this month, O'Sullivan's name typically is listed last. He's a career backup out of UC Davis who has changed rosters so often that he already has been on a quarter of the NFL's teams. The assumption is that O'Sullivan, who signed a one-year deal with San Francisco, will be the 49ers' No.3 passer if he makes the team at all.

Martz, however, sees the situation differently.

He insisted this week that O'Sullivan has a good chance of edging out Shaun Hill and Alex Smith and beginning the season atop the quarterback pecking order.

"He's capable of being a starter in this league," Martz said. "He's not a reliever, if you will. He's not a backup. He'll take full advantage of (the competition). He's a very fierce competitor."

After all, pedigree is not important to Martz.

Of his four most famous students Bulger, Kurt Warner, Trent Green and Jon Kitna, Bulger entered the league with the most fanfare. He was a mere sixth-round pick in 2000. O'Sullivan was a sixth-round pick by New Orleans in 2002.

In 2004, the Saints traded him to Green Bay for cornerback Mike McKenzie. But when Aaron Rodgers unexpectedly fell to the Packers in the first round of the 2005 draft, O'Sullivan became expendable.

He was picked up by the Vikings later that year and seemed to have found an advocate in Minnesota head coach Mike Tice. Tice, however, was fired at the end of the season and replaced by Brad Childress.

Said O'Sullivan: "I guess the nice way to put it is that I wasn't in their plans."

His break came in 2007 with Chicago. He made the Bears promise that if he didn't fit there, they would release him before training camp. They did and Martz pounced.

Now O'Sullivan enters the 2008 season in perhaps the best position of his career.

Smith and Hill are coming off of injuries and O'Sullivan is the only one of the three well-versed in the 49ers' new offense.

What's most important is that he has a major backer in Martz.

O'Sullivan didn't take part in the Lions' offseason program last year. He joined the club a month before the season but still picked up the system quickly enough to earn the No. 2 spot and get into the first regular-season game of his career an overtime win over Minnesota in Week 2.

That learn-on-the-fly ability told Martz that O'Sullivan was sharp. That he has hung around the league for six seasons reminded Martz of Warner, Bulger, Kitna and others.

"They just seem to have a certain persistence," Martz said. "It's like they're kind of on a mission. There's a sense of toughness that they've developed along the way. That's important."