If optimism alone were the key to success, then the addition of Carlos Silva has the Seattle Mariners believing they’re much better prepared to challenge the L.A. Angels in the American League West in 2008.

Maybe they are, but it will take more than Silva. And with that, the Mariners now enter the dicey part of their offseason.

To get Silva, the M’s will shell out $48 million over the next four years. To get the next starter — Orioles left-hander Erik Bedard, perhaps? — it will take many of the Mariners’ top young prospects.

While it has seemed clear since the Bedard rumors began that the Mariners will have to trade much of a group including pitcher Brandon Morrow, outfielder Adam Jones, pitcher George Sherrill and catcher Jeff Clement to the Orioles for Bedard, M’s general manager Bill Bavasi dropped a big hint as to who may go and who may not.

Bavasi says Morrow is so valuable as either a starting pitcher or late-inning reliever that “he’s highly, highly unlikely to go.” If Bavasi sticks to that gun, then it means Jones surely is gone if the M’s make that trade.

So, let’s say the M’s trade away Jones to get Bedard. Who’ will play right field, where Jones was to be the starter? Bavasi says Wladimir Balentien, whose big bat was impressive in the minor leagues, may not be ready for the majors.

The most likely outlet for outfield help is free agency, and there are some interesting names out there. One that already has spurred discussion in the Mariners’ offices is Brad Wilkerson, who hit 20 home runs in 2007 while splitting time between first base and the outfield for the Texas Rangers. Bobby Kielty, who suffered through an injury-filled season with the A’s and Red Sox, also is a free agent, as is Scott Podsednik of the White Sox and Mike Cameron of the Padres.

Mariners fans would welcome Cameron back with much love, at least until he heads down the road toward 150 strikeouts. Putting him in the same lineup with Richie Sexson would be painful.

And if Sherrill leaves, who takes over the left-handed setup role? There are three left-handed possibilities in-house — Ryan Rowland-Smith, Eric O’Flaherty and Ryan Feierabend. Against left-handed hitters, none of them was Sherrill-like. While leflties batted .240 this year against Sherrill, they batted .278 off O’Flaherty, .322 off Rowland-Smith and .431off Feierabend.

The Mariners go into the holidays with a big part of their offseason work completed with the addition of Silva. It’s unlikely any moves will be made between Christmas and New Year’s Day, which typically is a quiet time in baseball.

But when everyone gets back to business next month, the Mariners may have to part with some valued players if they hope to complete their starting rotation. It’s going to be a fun New Year.