SANTA CLARA — It should surprise no one if the 49ers trade up from their 31st overall slot in Thursday night’s first round of the NFL draft.

Mobility and unpredictability aren’t just the 49ers’ hallmarks on the field but also in the draft room, where each April they play a high-stakes version of Chutes and Ladders.

The fact they have 13 draft picks — and far fewer available roster spots — only enhances trade possibilities.

“We’re trying to stay ahead of the game from a picks standpoint,” general manager Trent Baalke said, “but we’re not opposed to moving up, minimizing the number of picks and getting the players that we want.”

Who would they want badly enough to move up in a potentially watered-down draft? Hint: Their positions of greatest need are free safety, defensive line, tight end, wide receiver and cornerback.

Although West Virginia wide receiver Tavon Austin has generated buzz for trade-up teams, the 49ers already used last year’s first-round pick on a wideout, A.J. Jenkins.

Quarterback Colin Kaepernick isn’t making any special requests, noting: “We have great players right now, so I’m going to leave that up to the front office.”

Those personnel wizards could be focusing on Justin Smith’s eventual replacement on the defensive line. Shoring up the secondary is a must after it was exposed in the playoffs, as well as after Pro Bowl safety Dashon Goldson’s departure to the Tampa Bay Buccaneers.

Like Kaepernick, Baalke is a read-option kind of guy, always angling to make his move. He’ll trade up, down, and up or down again to keep the 49ers what they are today: a perennial Super Bowl contender.

“We’ve always said we’re going to build this team through the draft, and you’re always trying to acquire picks,” Baalke said.

The 49ers’ Chutes-and-Ladders reputation comes from Baalke’s three-draft record.

In 2010, he traded up two spots to grab left tackle Anthony Davis 11th overall, and Baalke later traded down 18 places in the third round to steal linebacker NaVorro Bowman.

A major encore to those moves came in 2011, when the 49ers scaled nine spots in the second round to nab Kaepernick. The reasonable cost of that move: three later picks to the Denver Broncos (second-, fourth- and fifth-rounders).

Two other key reserves came out in other 2011 draft moves: The 49ers traded down to get cornerback Chris Culliver in the third round, then up to get offensive lineman Daniel Kilgore in the fifth.

Last season’s draft became a virtual sell-off after the selections of wide receiver Jenkins (30th) and running back LaMichael James (61st). Four trades followed, and the final one saw the 49ers move back up in the fourth round to draft guard Joe Looney.

Before Looney’s selection, a draft-room camera showed Baalke reacting in dismay when the Baltimore Ravens selected center/guard Gino Gradkowski in the fourth round. (The 49ers are the only NFC West team not allowing an NFL Network camera inside this year’s draft room.)

The 49ers’ 2013 war chest reached 14 total picks after they received the Kansas City Chiefs’ second-round selection (No. 34 overall) as part of the Alex Smith trade. But the 49ers eventually sent a sixth-round pick to the Cleveland Browns for quarterback Colt McCoy.

The 49ers haven’t drafted 13 players since 1991, when the draft lasted five more rounds (and their picks included Ted Washington, Ricky Watters and Merton Hanks).

Baalke said last week that the “wheeling and dealing” could begin any time. Even if no deals are yet in place, Baalke has become adept at improvisational deals.

“He’s old school, from where you’ve got to let it flow and come to you,” said Tom Gamble, the 49ers’ former director of player personnel who recently left for a similar role as an Eagles vice president. “There’s no cookie cutter way to do it.”

For more on the 49ers, see Cam Inman’s Hot Read blog at blogs.mercurynews.com/49ers. Follow him on Twitter at twitter.com/CamInman.