SANTA CLARA -- Rookie center Marcus Martin became the latest in a string of 49ers to suffer knee injuries in the past month. Martin had to be carted off the field after his left knee was injured on a fourth-quarter block in Sunday's exhibition win over the San Diego Chargers.

"What don't kill me, will only make me stronger," Martin wrote on Twitter. "I'll be back better than ever before, thank you everyone for the well wishes!! Love y'all!"

Coach Jim Harbaugh said afterward he did not know the severity of the injury. Martin's legs got rolled up on at the end of a Glenn Winston run, and before Martin got carted off the Levi's Stadium's field, a large contingent of teammates lined up to wish him well.

The 49ers have lost four players to season-ending knee injuries since training camp began: running back Kendall Hunter, guard Fou Fonoti, wideout Chuck Jacobs and linebacker Blake Costanzo.

Martin, a third-round pick out of USC, was hindered by an ankle injury during training camp, virtually eliminating him from contention for the starting center job with Daniel Kilgore.

  • Tight end Vance McDonald called it a "great honor" to score the 49ers' first touchdown in Levi's Stadium, never mind that it came in an exhibition game. After all, he had just eight catches for 119 yards and no touchdowns as a rookie.

    "I caught a lot of heat for that last year," said McDonald, a second-round draft pick out of Rice. "I never lost my confidence. I always knew I was capable of catching the football."


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    McDonald had a team-high three receptions for 29 yards in Sunday's 21-7 win. He gave the 49ers the lead, at 10-7, when he caught a 6-yard pass from Blaine Gabbert 46 seconds before halftime. "Blaine went out today playing really confident, coming off the last two weeks, he was firing the ball and found me open," McDonald said.

  • Levi's Stadium's replacement sod, which was installed Friday, didn't take long to make an impact. LaMichael James said he tweaked his left ankle on the opening kickoff when his foot slipped on the sod.

    James remained in the game, had seven carries for 9 yards and an 11-yard kickoff return. Harbaugh said James' carries went "too wide" at times.

    Rather than blame the sod, James said he should have worn better cleats. His footing didn't give way, however, when he nicely executed a couple pass-protection blocks. "I'm proving to y'all I can pass protect," James said. "Everyone doubts me, and I take it personal."

  • Harbaugh did not approve of Quinton Patton's emphatic celebration after his first catch of the exhibition season, a 10-yard conversion in which he had his helmet dislodged by a defender. "We don't want to see that," Harbaugh said of Patton's demonstrative strut toward the crowd. "I talked to him about that."

  • Rookie defensive back Jimmie Ward, the 49ers' first-round draft pick, intercepted a third-quarter pass. He had a potential touchdown return of a fumble nullified when officials ruled it an incompletion and upheld that call after a replay challenge.

  • The 49ers defense started its probable Week 1 lineup, with the exception of strong safety Antoine Bethea (concussion). Bethea's replacement, Craig Dahl, gave up a touchdown pass to a tight end for the second straight week, this time to Antonio Gates to put the 49ers behind 7-0.

  • Gabbert, who entered with the NFL's 112th-ranked passer rating of 17.9, posted a 110.4 rating (7 of 11, 66 yards, touchdown, no interceptions or sacks).

  • Wide receiver Michael Crabtree's first catch of the exhibition season came on a 10-yard strike Colin Kaepernick threaded between two defenders on a second-quarter field-goal drive.

  • Adam Snyder saw time at right and left guard with the first string. Jonathan Martin again started in place of right tackle Anthony Davis, who worked out before the game and isn't expected to play until Week 1 because of a shoulder injury.

  • Special-teams ace Bubba Ventrone (hamstring) and fullback Will Tukuafu (concussion) did not return from their injuries.

  • Cornerback Chris Culliver made two solid plays in a three-snap sequence, batting away a deep pass and making a sideline tackle.

  • The 49ers defense allowed no points on its opening series for the first time this preseason. Safety Eric Reid made a third-down tackle a yard short of the first-down marker.