How things have changed for the team that just regained sole possession of the NL wild card lead.Tulowitzki and the surging Rockies try to pull off a series win over their closest challenger for the wild card as they host the San Francisco Giants on Sunday afternoon.With the Rockies a then-season-low 10 games below .500 (18-28), Tulowitzki was batting .227 with five homers and 15 RBIs when Hurdle was let go May 29. Since Jim Tracy took over as manager, however, the 24-year-old shortstop is hitting .277 with 13 home runs and 30 RBIs while the Rockies have gone 35-16."If you look how we started and where we are now, its definitely a huge turnaround," Tulowitzki told the Rockies' official Web site earlier this month.After hitting .167 (4 for 24) in his first six games against San Francisco this season, Tulowitzki went 3 for 4 with a three-run homer and a career-high five RBIs in Saturday's 8-2 victory that gave Colorado (53-44) a one-game lead over the Giants."He really hit that ball and obviously hit it the other way," Tracy said of Tulowitzki's team-leading 18th home run. "It took just a great at-bat. When you see Troy Tulowitzki hitting balls with authority that way is when you know he's locked in. That's when he does the most damage."Tulowitzki's last homer came in the second inning of Tuesday's 6-5 loss to Arizona. Colorado staked Aaron Cook (9-3, 3.94 ERA) to a three-run lead in that frame, but the 30-year-old right-hander couldn't hold it even though he avoided taking his first loss since June 1.Cook returns to the mound Sunday after allowing four runs and eight hits over 6 2/3 innings."That was a tough one because you feel like when you get up by three runs, we should have been able to put it away," Cook said. "I feel like I got a couple of pitches up and they capitalized and it's just a tough team loss."Prior to Tuesday, Cook was 6-0 with a 2.56 ERA in his eight previous starts.He is 6-8 with a 5.06 ERA in 18 starts against the Giants but hasn't faced them since last season.San Francisco (52-45) closes a 10-game trip with rookie Ryan Sadowski (2-2, 4.15) on the mound. Called up from Class A San Jose, the 26-year-old right-hander was chased after 3 2/3 innings in Tuesday's 8-1 loss at Atlanta."My command was bad and my stuff was bad," Sadowski said after surrendering eight runs and eight hits in his first start since July 8.Since winning his first two career starts, Sadowski is 0-2 with a 10.38 ERA. Opponents are hitting .371 against him in his last two starts."One of the negative things that happens, when you go on such a good run like I was on, is when things start coming apart, you've got to be tough enough not to break down mentally. And I definitely did," Sadowski told the Giants' official Web site.Sadowski makes his first start against Colorado.Right fielder Brad Hawpe went 2 for 3 on Saturday when the Rockies improved to 19-8 at home since Tracy took over. Hawpe is batting .345 at Coors Field in 2009.Called up from Double-A Tulsa on Friday, Colorado right-hander Jhoulys Chacin made his major league debut Saturday by striking out two and walking one in a scoreless ninth inning.