When the 49ers gave Daniel Kilgore a three-year contract extension in February, it signaled that he would be their starting center for 2014 and possibly beyond. That plan remains intact despite the 49ers using an early third-round pick this month on USC center Marcus Martin

“Right now, he’s going to be in the understudy role,” Jim Harbaugh said of Martin. “That’s the expectation that we put on him -- to learn and get up to speed as fast as possible, and (we) put no timetable on it. That’s his expectation right now. Learn the offense.”

The 49ers ended the 2013 season with nine offensive linemen on the active roster. Two of them, Joe Looney and Ryan Seymour, typically were not in uniform on game days. Two more, Kilgore and Adam Snyder, served as backups on game days and appeared in the team's heavy jumbo packages.

As of now the starting unit for Week 1 would look like this:

LT Joe Staley

LG Mike Iupati

C Daniel Kilgore

RG Alex Boone

RT Anthony Davis

Martin said he will practice at center and both guard positions this offseason. He seems virtually assured of a roster spot and could fill the role Kilgore was in the past two seasons. You have to think that newcomer Jonathan Martin, because of his experience at tackle, also would win a spot and be active on game days. That means that everyone else, including Looney, Seymour, versatile Snyder, tackle Carter Bykowski and guard Al Netter, are competing for one – maybe two – more spots.

The 49ers, of course, also have to look ahead to next season. Iupati becomes a free agent in March and he could become the highest-paid guard in the league, a salary that would upset the 49ers' offensive line hierarchy and one the team might be unwilling to pay. If Iupati moves on? The team likely is eying Martin or Kilgore or Brandon Thomas for that spot. Thomas was considered a possible late first- or second-round pick before tearing an ACL in April. The 49ers took him with the final pick in the third round, and he should be ready to play at this time next year.

Looney also has practiced at guard and center in the past and could in the mix to be a backup at both spots. Seymour also has versatility. In that way, he and Looney could be competing for the same spot.