Brett Anderson, though, has been stellar.The left-hander looks to remain unbeaten when he faces the host Seattle Mariners and their own sizzling starter, Hisashi Iwakuma, on Saturday night.Anderson (3-0, 0.90 ERA) has looked every bit refreshed after a 14-month layoff following Tommy John surgery, giving up two runs in 20 innings while winning each of his starts.He gave up one run in six innings of Sunday's 6-2 victory over Boston for the Athletics (77-60), who are atop the AL wild-card standings and ended a three-game skid with a 6-1 win over Seattle on Friday."This all makes (the rehab) worthwhile," Anderson told the team's official website. "It couldn't be going better right now. You always gotta be confident. I thought I could come back and pitch well if I was healthy, and I've been able to do that and hopefully continue to from here on out."Anderson has helped boost a pitching staff that lost Colon to a 50-game suspension Aug. 22, and it now must contend with McCarthy's absence for an unknown amount of time while he recovers from a skull fracture after being hit in the head with a line drive Wednesday."To give us three games with that type of performance, coming into the later part of the season, and pitching in key games and not just getting ready for next season, it's all really impressive," manager Bob Melvin said of Anderson.Anderson seemingly has a good chance to continue his run, as he's 4-1 with a 0.96 ERA in his last seven starts against the Mariners (67-72), who look to bounce back with help from their rookie right-hander.Iwakuma (6-3, 3.14) has won his last four decisions, going 3-0 with a 0.35 ERA over his last four starts. He tossed 7 1/3 scoreless innings and struck out seven in a 2-1 win over the Los Angeles Angels on Sunday, and he's given up one earned run in his last 26 innings."Arguably, this might have been the best stuff we've seen him have," manager Eric Wedge told the team's official website. "He's had some other real good games, as well, but I think when you talk about that lineup and how aggressive he was and how he used all of his pitches, you just can't say enough about the performance he gave us."In Iwakuma's last appearance out of the bullpen before entering the starting rotation, he gave up a run in 3 2/3 innings and suffered a 2-1 loss to Oakland on June 27.Oakland has won four of the last five meetings with Seattle, with the Mariners scoring one run in each of their defeats. George Kottaras hit a three-run homer Friday as the A's chased Felix Hernandez after 4 2/3 innings."Those things (McCarthy's injury) are going to happen," Kottaras added. "You try to turn the page, take one game at a time, the past is the past. We came here and played hard like we always do and put some good at-bats together and came out on top today."Seattle, batting a major league-worst .232, has scored fewer than four runs in six of its last seven games.