SANTA CLARA – The battle to be Alex Smith's backup still hasn't been decided, but Colin Kaepernick will be the first quarterback off the bench in Friday's exhibition opener against the Vikings, coach Jim Harbaugh said Monday.

Backup quarterback is one of the few unsettled positions on a deep, experienced 49ers roster. Harbaugh has said there's a tie among Kaepernick, Josh Johnson and Scott Tolzien for the job.

All three see about the same amount of practice time in training camp, although Kaepernick usually gets the first chance to operate with the second-team offense. Harbaugh said Kaepernick is ahead of the others but that he needs to see them in preseason games to make a final decision.

Kaepernick was Smith's backup last season but threw only five passes, connecting on three for 35 yards, all season. He appeared in three games, including mop-up duty at the end of a blowout win over the Rams on Dec. 5.

"He's going to get a lot of work, a lot of game work," Harbaugh said. "They all need it. They're all fighting for that job. The competition, as I said, is very close.

"Colin, specifically, needs that work," he continued. "It's been a long time since he's played in game action. You kind of liken it to a golfer who does nothing but play the same course over and over and over again. That's kind of what practice can be like for a quarterback."

Harbaugh wouldn't commit to a snap total for Friday's game. He said each quarterback would play a "good amount."

All of the quarterbacks, including Kaepernick, have struggled against the 49ers' defense in recent practices, and some of the defensive backs poked fun at Kaepernick for his tendency to tuck the ball away and run with it when his first options are covered.

During a four-minute drill Monday, however, Kaepernick had the last laugh.

The object was for the offense to run out the clock in an end-of-game scenario. Facing third and long, Kaepernick hit rookie wide receiver A.J. Jenkins along the sideline on a comeback route for a first down that allowed the offense to run out the clock.

"I think he's made some real progress," Harbaugh said when asked about Kaepernick's decision to run or throw the ball. "It's been noticeable in practice."

Crabtree's return – For the first time since the start of training camp, wide receiver Michael Crabtree was in full pads and participated in individual drills Monday. That, however, was the extent of the action as the receiver observed the rest of the session, including seven-on-seven and team drills.

Harbaugh said Crabtree's calf injury would be re-evaluated today to determine whether to ramp up his participation.

Crabtree is listed as a starter at wideout in the depth chart the team released Monday, although his status for Friday's game is still fuzzy. At the other wide receiver position, the starter is listed as "Randy Moss or Mario Manningham or Ted Ginn Jr." Kyle Williams is listed behind Crabtree.

Et cetera – Starting left guard Mike Iupati and tight end Nate Byham were back at practice after missing the past two days. Iupati was home for the birth of his first child.

• Nose tackle Isaac Sopoaga worked with the offense at times Monday. Sopoaga saw 42 snaps on offense, mostly as a fullback, last season.

• Defensive back Cory Nelms' longtime girlfriend, T'erea Brown, will run in the Olympic finals of the 400-meter hurdles Wednesday. Nelms and Brown ran track at the University of Miami.

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