The Twins have called up catcher Rene Rivera from triple-A Rochester to backup Drew Butera.  The team sent down catcher Steve Holm after Wednesday's game.  Holm was hitting .118.  Rivera is 27 years old and was hitting .200 with 1 homerun and 6 RBIs at triple-A Rochester.  He appeared in 53 major league games with Seattle from '04-'06.  The Twins chose Rivera over prospect Danny Lehman.  Lehman was hitting .280 at triple-A.  The Twins begin a 4-game series at Boston against the Red Sox tonight at 6:10, pregame on WJON at 5:40.  Righthander Scott Baker (1-2) gets the start on the mound for the Twins and knuckleballer Tim Wakefield gets the ball for the Red Sox.  The Twins are 11-18 and have won 2 straight.