SAN DIEGO -- One of the 49ers' last roster questions got answered even before kickoff of their exhibition finale against the Chargers.
Seneca Wallace told the 49ers on Thursday morning he's decided to halt his comeback attempt, according to general manager Trent Baalke.
Signed only a week ago, Wallace's departure turned the No. 3 quarterback race into a one-man competition for rookie B.J. Daniels, if the 49ers indeed go with a three-man unit.
The 49ers have kept three quarterbacks in each of Jim Harbaugh's two seasons as coach. They must trim their roster from 75 to 53 by 1 p.m. Saturday, and they were weighing how to term Wallace's transaction, as a retirement or a terminated contract.
More pertinent to the 49ers' quarterback cause, starter Colin Kaepernick emerged healthy after playing sparingly all exhibition season.
Kaepernick made a one-series cameo Thursday -- as was the case in the first two exhibitions -- and exited after Quinton Patton's 43-yard, catch-and-run touchdown for a 7-0 lead.
Kaepernick wasn't sacked in any of his six exhibition series, and he finished 15 of 24 for 171 yards, with two touchdown passes, no interceptions and a 116.4 passer rating.
Settling on Kaepernick's backups looked like a convoluted situation a week ago, when Wallace's addition gave the 49ers a five-man quarterback crew.
Wallace, who did not play last season, took the final three snaps of Sunday's exhibition and completed his only two passes for 27 yards.
Cut last week by the New Orleans Saints, Wallace joined the 49ers as a veteran option. But Colt McCoy restructured his contract Saturday night and subsequently was named the No. 2 quarterback by Harbaugh after Sunday's rout of Minnesota.
McCoy replaced Kaepernick after one series Thursday night, and after showing off his mobility on a few scrambles, McCoy threw his first touchdown in a 49ers uniform, a 5-yard pass to Anthony Dixon.
Daniels, a seventh-round draft pick, is in line to succeed Scott Tolzien as the No. 3 quarterback behind Kaepernick and McCoy. Tolzien was released Monday after two seasons in that No. 3 role. Patton, starting in place of Anquan Boldin, impressed beyond his second touchdown catch in the past two exhibitions. He also had a 9-yard catch to open the 49ers' second series, and he averaged 34.5 yards on two kickoff returns, both of which he fielded deep in the end zone. All of the 49ers' projected Week 1 defensive starters got the night off except for nose tackle Ian Williams. The rest of the makeshift lineup: Corey Lemonier, Will Tukuafu, Demarcus Dobbs, Nick Moody, Michael Wilhoite, Tramaine Brock, Perrish Cox, Craig Dahl and Trenton Robinson. LaMichael James exited in the second quarter with a left-knee injury that's not believed to be serious. James had two carries for minus-4 yards and a 10-yard punt return. He left Sunday's game with an elbow injury. Adam Snyder, arguably the 49ers' top backup offensive lineman, left in the second quarter for an X-ray on his hand. Snyder has been the second-string right guard but also has experience at every other position on the line. Two days after trading away Parys Haralson, the 49ers got first-half sacks from each of their remaining backups at outside linebacker: Dan Skuta, Lemonier and Cam Johnson, who added a second sack just before halftime. By bulling his way across the goal-line on that 5-yard touchdown pass from McCoy, Dixon recorded his first career receiving touchdown, be it in the exhibition, regular or post-seasons. Wilhoite's second-quarter interception set up Dixon's touchdown. Jon Baldwin failed to haul in a potential 11-yard touchdown pass by McCoy midway through the second quarter. Not present was linebacker Patrick Willis, who sat out the exhibition season with a broken hand. He returned to practice last week and is expected to play in the season opener. Kendall Hunter started in place of Frank Gore and had three carries for 13 yards on the opening series. Kevin McDermott, who has competed with Brian Jennings, handled the long-snapper duties. Because of local airport curfews, the 49ers planned to bus over 1½ hours and fly out of Ontario Airport. Budget cuts prevented them from flying out of a local military base, as they did in 2011. As was the case before their 2011 exhibition finale here, the 49ers held a walk-through practice at the University of San Diego, where Harbaugh held his first head-coaching job from 2004-06. Rookie running back Marcus Lattimore has teamed with Tide detergent as the 49ers' representative to post behind-the-scene pictures from this season on his Twitter account (@MarcusLattimore).