The Tampa Bay Devil Rays today moved to bolster their pitching staff, acquiring reliever Tyler Walker from the San Francisco Giants for minor-league right-hander Carlos Hines. To make room on the roster, the Rays designated right-hander Scott Dunn for assignment. The Rays have 10 days to trade, release or re-assign Dunn. Walker, 29, filled in as the Giants' closer last year when Armando Benitez was lost for the season with a knee injury. He was 6-4 with 23 saves in 67 appearances last year, but was designated for assignment Sunday after going 0-1 with a 15.19 ERA in 5 1/3 innings this season.