The San Francisco 49ers acquired one Pro Bowl left tackle and said goodbye to another.

The defending NFC champion 49ers acquired seven-time Pro Bowl left tackle Trent Williams from the Washington Redskins on Saturday for a pair of draft picks and later announced that six-time Pro Bowler Joe Staley is retiring.

The Niners sent a fifth-round pick in this year’s draft and a 2021 third-rounder to acquire Williams, who still must pass a physical for the trade to be finalized.

The 49ers had a big need at left tackle because Staley informed them he planned to retire. He announced it later Saturday, saying a deteriorating neck injury led to his decision to retire after 13 seasons. Staley also missed nine games last season with injuries to his leg and finger.

“The game of football has been a true passion of mine since I was 8, but my body is telling me it is time,” Staley said in a statement. “Football is a physical sport and I have given my all to the game and pushed my limits. Last season was a dream to be a part of, having the opportunity to chase a championship. But, it was by far the most difficult on me and my family.”

Staley was a first-round pick in 2007 and played 181 games over 13 seasons. He was selected to the NFL's all-decade team for the 2010s and played a big role in San Francisco's runs to the Super Bowl following the 2012 and '19 seasons.

“A consummate professional, one of the best players in the game and a great human being, Joe has left an indelible mark on this franchise and everyone he has come into contact with throughout his career," 49ers CEO Jed York said.

“His passion, sense of humour and heart are just a few of the many traits that allowed him not only to be a team leader but also an ambassador for our game and the Bay Area.”

Staley leaves a big void but the 49ers managed to find a more than suitable replacement.

Williams sat out the entire 2019 season because of a dispute with Washington’s front office. The Redskins did not trade him before the Oct. 29 deadline and Williams renewed his request for a trade this off-season.

In November, Williams revealed he had cancer and said that situation led him to distrust the Redskins’ medical staff and organization as a whole. The 31-year-old at the time said “there’s no trust there” with president Bruce Allen, who was fired after Washington’s 3-13 season.

The medical staff also was overhauled, and new coach Ron Rivera took control of football operations. Rivera spoke with Williams and it seemed as if there was hope to repair the relationship.

Instead, the Redskins gave Williams’ representatives permission to seek trading partners and it led to the deal with San Francisco on the third day of the draft.

Williams' agent, Vincent Taylor, said in a statement that it was time for Williams to leave Washington.

“Trent Williams is ready to get back to competing in the NFL and is glad to be part of a great organization like the San Francisco 49ers," Taylor said.

The deal reunites him with 49ers coach Kyle Shanahan, who was the offensive co-ordinator in Washington when Williams was drafted fourth overall in 2010.

Williams made the Pro Bowl every season from 2012-18 and is considered one of the best left tackles in the league when healthy. He has one year remaining on his contract, which will pay him $12.5 million this season.

The acquisition of Williams is the biggest veteran addition this off-season for the defending NFC champion 49ers. They spent free agency trying to keep the team together, reaching deals with defensive lineman Arik Armstead and safety Jimmie Ward.

They then drafted defensive tackle Jevon Kinlaw and receiver Brandon Aiyuk in the first round to replace the departed DeForest Buckner and Emmanuel Sanders. Now they have added one of the top tackles in the league.

Minutes after completing the trade, the Redskins drafted Williams’ potential replacement, LSU lineman Saahdiq Charles, with the 108th pick.

“Growing up as an offensive lineman, I watched Trent’s film many a time, and I have a lot of respect for his game,” Charles said. “Just to see that they traded him and picked me, it just shows what they might have in mind for me. I’m going to come in there (with) hard work and go do my thing.”