DETROIT -- The 49ers, who hadn't scored a first-quarter touchdown all season, did so Sunday largely on the legs of newcomer running backs DuJuan Harris and Jarryd Hayne. The Lions lead 20-17 thanks to a last-second, 38-yard field goal at the end of the half.
Hayne, who was elevated from the practice squad Saturday, was a surprise starter and had three carries for 15 yards on the first drive, including a season-high 11-yard run on which he broke two tackles.
The real playmaker was Harris, who wasn't even a 49er at this time last week. He had three runs for 33 yards -- including a 22-yard gain on third and 1 -- on the opening drive. Harris, who was signed off the Ravens practice squad Tuesday, also had one catch for 11 yards and has a career-high 74 yards at halftime
The opening drive also included three catches for Anquan Boldin, who became the 13th NFL player ever with 1,000 receptions for his career. A pass interference call on a throw to Torrey Smith in the end zone gave the 49ers a first-and-goal scenario at the 1-yard line.
On the next play, Blaine Gabbert used a play-action fake, then found Vance McDonald in the end zone for the tight end's third touchdown of the year. Gabbert was 5-5 on the drive.
He went in Smith's direction the next time the 49ers were in the red zone, this time on a second-and-8 scenario in the second quarter. Smith caught the ball in front of the goal line, then crashed into the end zone for a 16-yard score. Gabbert is 12-18 for 154 yards and two touchdowns. His halftime passer rating is 130.3.
The next drive didn't end as well.
The 49ers began it deep in their own territory because of a special teams penalty, one of several mistakes by that unit early on. On third down, Gabbert was sacked by Haloti Ngata, who beat center Daniel Kilgore on the play. The second defender in, linebacker Josh Bynes, knocked the ball free and Detroit recovered at San Francisco's 1-yard line.
On the next play Joique Bell easily ran in for a touchdown and a 17-14 lead for the Lions.
On defense, Dontae Johnson started the game at right cornerback, presumably because his 6-2 height offered a better matchup against Lions 6-5 receiver Calvin Johnson. Detroit targeted Dontae Johnson early on with an eight-yard completion to Calvin Johnson. But an end-zone attempt later in the drive was knocked away nicely by the 49ers cornerback.
Johnson, however, was in coverage on Detroit's first touchdown, a 29-yard pass from Matthew Stafford to receiver T.J. Jones.
That drive included a neutral-zone foul by San Francisco -- they had six neutral zone of offsides penalties in the half -- as well as a successful fake punt by the Lions on fourth and 1.
The 49ers defense also lapsed at the end of the half. With only 20 seconds left, nickel cornerback Jimmie Ward lost track of receiver Golden Tate, who gained 36 yards and set up the Lions' go-ahead field goal. The pass play was the longest play of the half for Detroit.