They played 15 postseason games in 2010 and 16 in 2012. They sent nine players to the World Baseball Classic last spring and six of them later suffered injuries. No one should be surprised that for the San Francisco Giants the bill finally is coming due. Still it’s difficult to believe that the defending World Series champions are in last place in the NL West 12 games under .500 10 games behind the division-leading Los Angeles Dodgers. The math as general manager Brian Sabean told San Francisco radio station KNBR last week is “horrific” and only getting worse. So Sabean according to major-league sources now will do something that he has done very rarely since becoming the team’s GM since 1997 — entertain trade offers for veteran players at the non-waiver deadline. Ideally the Giants would like to keep three of their potential free agents — right fielder Hunter Pence right-hander Tim Lincecum and left-handed reliever Javier Lopez. But at this point club officials feel they must listen to any reasonable proposal sources say. Lopez holding left-handed hitters to a .172 batting average and .466 OPS probably is the most likely to go. He could appeal to Cleveland Atlanta and a number of other clubs looking for lefty specialists. Lincecum who has struck out 10 or more in three of his past four starts including a no-hitter would be a more complicated transaction. He is highly popular in San Francisco and owed nearly $8 million of his $22 million salary. Then there is Pence who in some ways is the trickiest call of all. The Giants already need to find a left fielder for 2014 and center fielder Angel Pagan will be coming off surgery to repair a torn left hamstring. A void in right only would create additional problems. The Giants acquired Pence from the Philadelphia Phillies at last year’s deadline for outfielder Nate Schierholtz Double-A catcher Tommy Joseph and Single-A pitcher Seth Rosin. A good move it was too helping the team win its second World Series in three years.