SPORTSTICKER NL PREVIEW SAN FRANCISCO (Ticker) -- The Houston Astros look to improve on the best record in the National League tonight when they begin a three-game series against the San Francisco Giants. Houston has won seven of its last nine games and has the best mark in the NL, a half-game better than the Atlanta Braves. The Astros have a 3 1/2-game lead over the Chicago Cubs in the NL Central. Sean Bergman (2-1, 4.81 ERA) takes the mound for Houston. Bergman is 2-0 in his last five starts. The righthander surrendered four runs and eight hits over six innings and did not have a decision against the Giants on Sunday. The Giants have lost four of their last six games, but are coming off Wednesday's 8-3 victory over Arizona. Despite playing without injured Barry Bonds, the Giants are still atop the NL West by a half-game over Arizona. San Francisco is 15-14 without Bonds, who is expected to miss at least another seven weeks with a damaged triceps tendon and bone spurs in his left elbow. A struggling Mark Gardner (0-4, 10.88) is on the mound for San Francisco. Gardner has lost his last four starts and was torched for nine runs -- eight earned -- and six hits over 4 1/3 innings in a loss at Houston on Saturday. Gardner is 7-5 against Houston lifetime. Houston has taken four of six games from the Giants this season.  