One down. Four to go?

The 49ers locked up one of their young stars with a soon-to-be-expiring contract today when they signed right tackle Anthony Davis, 23, to a five-year extension that will keep the No. 11 pick in the 2010 draft in San Francisco through 2019. The extension, first reported by ProFootballTalk, is worth $37.295 million with $17 million guaranteed.

Before the extension, Davis was among a quintet of frontline players under 26 who were signed by the 49ers through 2014. The others: quarterback Colin Kaepernick, outside linebacker Aldon Smith, wide receiver Michael Crabtree and left guard Mike Iupati, who was selected six picks after Davis in 2010. The 49ers can’t work out extensions with Kaepernick and Smith until after the 2013 season.

In keeping with their philosophy of retaining their own talent, the 49ers will presumably make a strong push to keep those other four players, who were each selected in the first two rounds of the draft. In November, they signed All-Pro inside linebacker NaVorro Bowman, 24, to a five-year, $45.25 million extension. Bowman’s contract was set to expire after this upcoming season.

In 2010, the 49ers traded a fourth-round pick to the Broncos to move up two picks in the draft and select Davis. The move was questioned as Davis, 20 when his rookie season began, struggled while starting 16 games in his first year. General manager Trent Baalke remained Davis’ staunchest supporter and the 2010 trade-up now looks inspired.