The Oakland Athletics acquired left-handed starter Jon Lester and left-fielder Jonny Gomes on Thursday from the Boston Red Sox, according to sources close to the situation. MLB.com confirmed the trade.

In return, Boston received left-fielder Yoenis Cespedes and Oakland's 2015 competitive balance draft pick. Neither the Red Sox nor A's have officially announced the deal, which was agreed to just ahead of the league's non-waiver trade deadline [ 4 p.m. ET].

Lester is 10-7 with a 2.52 earned-run average and 149 strikeouts this season. He can become a free agent after this season.

The 30-year-old Lester was in his ninth season with the Red Sox - the team that drafted him in 2002. Boston is the only team Lester has played for in the majors.

Last year, he expressed a desire to remain with the club during contract negotiations. But talks ended when Lester rejected a four-year, $70 million offer.

Acquiring Lester is risky for Oakland. He recently told reporters that despite the possibility of being traded, he would remain open to re-signing with Boston as a free agent.

Cespedes, an aggressive batter, provides a solid slugger to complement David Ortiz in its lineup. He has a .257 average with 17 homers and 67 RBIs this season.

The drawback is that Cespedes oftentimes lacks discipline at the plate: He has worked out just 28 walks and has struck out 80 times.

Gomes is batting .234 with six HRs and 32 RBIs this year.