Updated

The Oakland Athletics have agreed to terms with free agent right-handed reliever Grant Balfour on an $8.1 million, two-year deal.

A person with knowledge of the situation confirmed the deal to The Associated Press on Friday but spoke on condition of anonymity because the contract will not be finalized until Balfour passes a physical. A formal announcement could come as soon as Monday.

Balfour is set to earn $3.75 million next season and $4 million in 2012. The deal includes a $4.5 million club option for 2013 with a $350,000 buyout.

The A's are boosting their already talented pitching staff a month before pitchers and catchers report to spring training in Phoenix.

The 33-year-old Balfour went 2-1 with a 2.28 ERA in 57 appearances for the Tampa Bay Rays last season, his seventh year in the big leagues.

Balfour will provide depth to a bullpen already featuring 2009 AL Rookie of the Year closer Andrew Bailey. While his role will be determined by manager Bob Geren come spring training, Balfour could fit into several different bullpen slots.

Right-hander Rich Harden is back with the A's, his original team, for 2011 likely as a reliever. The fifth starter job will be open to competition this spring. Brett Anderson, Dallas Braden, Trevor Cahill and Gio Gonzalez are penciled in for the rotation.

It's been quite the busy winter for Oakland general manager Billy Beane, who has made several significant upgrades to his roster in hopes of contending in the AL West in 2011. They were runner-up in the division to the AL champion Texas Rangers last season.

Japanese slugger Hideki Matsui received a $4.25 million, one-year contract last month to give the A's a power bat in the middle of the order.

Oakland acquired outfielder David DeJesus in a trade with the Kansas City Royals in November, then picked up another corner outfielder in Josh Willingham in a swap with the Washington Nationals in mid-December.

Willingham is another middle-of-the-order hitter who should complement Matsui and DeJesus.

The A's stayed in the AL West chase until late in the season, finishing 81-81 for second place in the division. That was despite using the disabled list 23 times, two shy of the franchise record set in 2008.

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AP Sports Writer Ronald Blum in New York contributed to this report.