Felix Hernandez may be the best pitcher in baseball, but you won't mistake any other Mariners starters for aces. Next year, some combination of current Seattle starters, prospects and free agent additions will likely follow Hernandez in the rotation. Here are the specifics.
We can safely assume that Jason Vargas and Doug Fister have earned tentative spots in next year's rotation. Vargas (3.55 ERA) and Fister (3.85 ERA) have been pleasant surprises in Seattle this year and will likely be back in the 2011 rotation.
Luke French and David Pauley have each started a handful of games for the M's this year, although it would be a surprise to see the Mariners hand either pitcher a rotation spot uncontested. French, who turns 25 later in the month, has a 4.13 ERA, but his strikeout rate (3.8 K/9), FIP (4.65) and xFIP (5.52) suggest his ERA is likely to rise. Pauley has a 51% ground ball rate, but he doesn't strike anyone out either (4.9 K/9). In fact, many Mariners starters have low strikeout rates; French, Pauley, Vargas and Fister all strike out 5.6 batters per nine or less.
The Mariners could turn to minor league right-hander Michael Pineda if they're looking to add another power arm to the rotation. The 21-year-old entered 2010 as the seventh-best prospect in the organization, according to Baseball America, and he has since had a tremendous season. Pineda posted a 3.36 ERA with 9.9 K/9 and 2.2 BB/9 in the upper minors and the Mariners will presumably give him every opportunity to win a rotation job next spring.
Mauricio Robles and Blake Beavan have pitched well since joining the Mariners in recent mid-summer trades (the Jarrod Washburn and Cliff Lee deals). Robles, 21, has struck out more than a batter per inning in the upper minors (9.9 K/9), but has major command issues (4.7 BB/9). Baseball America suggested before the season that he could be a back-of-the-rotation starter, but Robles' future could just as easily be in the 'pen. Beavan, a 21-year-old right-hander, has flashed excellent command in the upper minors (1.1 BB/9), but like so many current Mariners, doesn't strike many opponents out (5.4 K/9).
Ryan Rowland-Smith will go to arbitration for the first time this winter, but with a 6.96 ERA and more walks than strikeouts, Rowland-Smith won't have much of an arbitration case if the M's tender him a contract. Seattle could bring the left-hander back (probably for less than $1MM) and add him to the bullpen.
The Mariners will presumably decline the options for Ian Snell ($6.75MM option, likely non-tender) and Erik Bedard ($8MM mutual option, $250K buyout). It wouldn't be a surprise to see the team sign a free agent starter, though. Hernandez is a proven innings eater, but Vargas, Fister, Pineda, French and Pauley are not sure things, so the team may well be interested in signing a veteran starter to a short-term deal this offseason.