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(SportsNetwork.com) - In a duel between former teammates, Scott Kazmir and the Oakland Athletics will face off with James Shields and the Kansas City Royals at O.co Coliseum.

Shields and Kazmir were both a part of the Tampa Bay Rays rotation from 2006-09, before Kazmir was traded to the Angels in the midst of the 2009 campaign.

Now eating up innings for Oakland, another team in the AL West, Kazmir has found the success that made him such a threat with Tampa Bay. Kazmir is 12-3 with a 2.37 ERA this season, with each of those marks having him on pace to smash his previous bests. In fact, with a win on Sunday, Kazmir would match his career high for wins in a season, which he set in 2007 as a 23-year-old.

Now 30, Kazmir has certainly reestablished himself. He only lasted five innings in his last outing, allowing two runs on five hits against Texas, but he had pitched seven innings in each of his previous three starts.

Kazmir has some familiarity with the Royals, a team he faced as a division rival last season while with the Indians. In 15 career starts against Kansas City he is 4-5 with an inflated 5.15 ERA.

Shields also left Tampa Bay via trade, one that brought 2013 Rookie of the Year Wil Myers to the Rays.

The 32-year-old right-hander has been effective for the Royals and he has also been a workhorse. He has a 3.29 ERA over the last two seasons and last year was tied for the AL lead in innings pitched (228 2/3).

This season he is currently sitting with a 9-6 record and a 3.50 ERA, while his 23 starts are tied for the most in baseball.

Unfortunately, Shields has lost three of his last four decisions, including his last start when the Royals fell 2-1 to Minnesota. Shields pitched fairly well in the game, allowing two runs, one earned, over six innings. However, he did tie a season high with four walks.

Shields owns a 5-4 all-time record against Oakland in 13 total starts. He also has a 3.91 ERA, but he is 2-3 with a 4.53 ERA in seven starts at O.co Coliseum.

Jon Lester made his debut in an Oakland uniform on Saturday and helped the A's earn an 8-3 victory. Lester allowed three runs on nine hits over 6 2/3 innings of work to improve to 11-7.

"I felt fine physically," Lester said. "Some times those extra days can help you or hurt you and it did a little bit of both for me today. I was a little sloppy with my cutter ... I would've liked to finish that seventh, but I got a little bit ahead of myself and I couldn't."

Johnny Gomes, who also came over from Boston on Thursday, went 2-for-4 with two RBI to help power Oakland on offense. The A's had lost three of four prior to Saturday's win, including a 1-0 setback against Kansas City on Friday.

Kansas City had won three straight before Saturday's loss, which went to Jason Vargas, who allowed seven runs in just 4 1/3 innings of work.

Oakland won five of six against the Royals a year ago.