In each of the last three seasons, manager Bruce Bochy slotted a left-handers between co-aces Tim Lincecum and Matt Cain in the season-opening rotation.It was Randy Johnson in 2009, Barry Zito in 2010 and Jonathan Sanchez last season. It's Bochy's way of separating his hard-throwing right-handers, an attempt to keep hitters off balance.The trend figures to continue this year. Another left-hander, Madison Bumgarner, seems destined for the No. 2 slot between Lincecum and Cain.The hope is for Ryan Vogelsong to overcome a strained back and return to the mound by the time the season starts, so he could assume his No. 4 spot. Zito would be the fifth starter. If Vogelsong isn't ready for the season, candidates to replace him are left-handers Eric Surkamp and Brian...