The floundering San Francisco Giants, who tumbled into last place in the National League West with their latest loss, might be making an ill-timed visit to Coors Field when they open a four-game series Thursday against the Colorado Rockies. The Rockies are 6-1 against the Giants this season. Colorado won three of four from April 3 to April 16 at Coors Field and swept three games from the Giants at At&T Park from April 21 to April 23, outscoring them 26-8 in that series.