PHOENIX (Interstat) — The St. Louis Cardinals and Arizona Diamondbacks, two teams jockeying for position in the National League wild-card race, open a pivotal three-game series Saturday afternoon at Chase Field. St. Louis (50-45) enters the game having lost two straight, including a 4-3 defeat Sunday to Atlanta. The Cardinals hold a slim one-game lead over the Diamondbacks (49-47) in the standings. Right-hander Dustin May is expected to be a key factor for St. Louis. May has been inconsistent over his past four outings. He took the loss July 12 against Atlanta, allowing two earned runs on two hits over four innings with four strikeouts. On July 6 against Milwaukee, he worked 4 ⅔ scoreless innings, scattering four hits and striking out seven, but did not factor in the decision. May’s two wins in that span came despite allowing a combined 11 earned runs over 2 ⅔ innings against Atlanta and Kansas City. For Arizona, closer Paul Sewald has been a steady force out of the bullpen. He earned the win Sunday at the Los Angeles Dodgers, striking out one in a perfect ninth inning. Sewald has allowed one earned run in his past three appearances, spanning three innings, with five strikeouts. However, he struggled in his last outing against the Cardinals on June 23 in St. Louis, yielding three earned runs on four hits in ⅔ of an inning. The Diamondbacks have won four of their past five games, including a three-game sweep of the Dodgers. Arizona took two of three from St. Louis in their last meeting, June 22-24 in St. Louis. The Cardinals dropped two of three to Atlanta in their most recent series. Saturday’s game is the first of four meetings between the clubs in the next six days. After Sunday’s game in Phoenix, the Cardinals travel to Los Angeles for a three-game set against the Angels, while the Diamondbacks host the Athletics. Arizona’s game simulator projects a 6-4 victory for the Diamondbacks. St. Louis is a 1.5-run favorite on the run line, and the over/under is set at 9 runs. First pitch is scheduled for 7:10 p.m. local time. UP NEXT: The series continues Sunday afternoon before the Cardinals head to Anaheim.