San Francisco 49ers

49ers acquire offensive tackle Jonathan Martin from Dolphins

The 49ers topped perhaps the busiest day for any NFL team on the first day of free agency by acquiring offensive tackle Jonathan Martin from Miami.

It wasn’t difficult to detect the 49ers’ interest in Martin when coach Jim Harbaugh, in the league report that documented Martin’s travails with the Dolphins, said he thought his former player could resume a productive NFL career.

On Tuesday, the 49ers followed through, trading a conditional seventh-round draft pick in 2015 to Miami for Martin, who was a second-round pick in 2012.

Martin, 24, doesn’t have to go far to join his new team. The former Stanford lineman, who was recruited by Harbaugh, has been taking classes at Stanford. Martin has played both right and left tackle, and he becomes a top candidate to become the so-called “swing tackle” who can back up either Anthony Davis at right tackle or Joe Staley on the left side. Last year that job fell to guard Alex Boone, with Adam Snyder also filling in at times at tackle.

Martin left the Dolphins in October amid allegations of bullying in the Miami locker room. A report that detailed “a pattern of harassment” among Dolphins offensive linemen included interviews with Harbaugh and current Stanford coach David Shaw. Harbaugh said Martin not only fit in well inside the Stanford locker room but that he didn’t think the 49ers’ locker room was all that different than Stanford’s.

“(Harbaugh) told us that he had never doubted Martin’s tenacity, work ethic and dedication to the game, and that he had never seen Martin exhibit problems with social adjustment,” the report commissioned by the NFL said. “Coach Harbaugh told us he believed that Martin likely could continue to have a successful career in the NFL.”

Martin has two years remaining on his original contract at base salaries of $825,000 and $1.04 million. He is expected to join teammates when the 49ers’ offseason conditioning program begins April 21.

In a very busy day, the 49ers also:

• Lost safety Donte Whitner to Cleveland as soon as free agency began. The Browns, who had more than $50 million of salary-cap space when the day began, signed Whitner to a four-year deal worth $7 million a season.

Even though Martin’s signing was the most high-profile move of the day for the 49ers, the loss of Whitner was the team’s most important transaction. Whitner, who started 55 of 56 games at strong safety the past three seasons, was a spokesman and leader on the defense and was rookie Eric Reid’s primary mentor in 2013.

It’s the second year in a row the 49ers have lost a starting safety in free agency. Dashon Goldson signed a five-year deal worth $8 million a season to play for Tampa Bay last year. Goldson and Whitner were known for hard hits but also costly penalties. The two were flagged a combined 13 times for 149 yards last year.

• Signed Antoine Bethea, an eight-year veteran, to replace Whitner. The former Indianapolis safety, who hasn’t missed a start since 2007, signed a four-year deal that will average between $5 million and $6 million a season. Bethea has averaged more than 100 tackles in four consecutive seasons and, like Whitner, he is better against the run than he is in coverage.

• Traded a sixth-round draft pick to Jacksonville for quarterback Blaine Gabbert, the 10th overall selection in 2011. Harbaugh attended Gabbert’s pro day workout three years ago. Now Harbaugh will attempt to resurrect the career of a quarterback who had a 66.4 passer rating for the Jaguars. The deal means Colin Kaepernick’s 2013 backup, Colt McCoy, is unlikely to return.

• Re-signed kicker Phil Dawson to a two-year deal. Dawson set a franchise record with 27 consecutive field goals last season and kicked the game-winner in the playoffs to defeat Green Bay. Dawson’s challenge this year is adjusting to a new stadium. “It’s very similar to the situation I was in last year where I had to go into a new stadium and figure it out,” he said. “I welcome that challenge.”

• Re-signed cornerback Eric Wright to a one-year deal. Wright, a San Francisco native, gives the 49ers some options at cornerback. Starters Tarell Brown and Carlos Rogers are testing the free-agent market. Of the cornerbacks currently on the roster, Wright is the only one with meaningful experience at the increasingly critical nickel spot.

• Tendered one-year contracts to defensive lineman Demarcus Dobbs and linebacker Michael Wilhoite. Wilhoite will compete with Nick Moody and others the 49ers bring in this offseason for the chance to fill in for NaVorro Bowman while he recovers from an ACL tear.