CHICAGO (AP) -- The Cincinnati Reds became the first team in the majors to clinch a playoff spot this season, beating the Chicago Cubs 5-3 Thursday while manager Dusty Baker remained in a hospital after being diagnosed with an irregular heartbeat.
Ace Johnny Cueto and the NL Central leaders ensured themselves of at least a wild-card spot. Cincinnati cut its magic number to two for winning the division for the second time in three years.
The Reds said Baker would remain in a Chicago hospital for an additional day so doctors could monitor his progress. He left Wrigley Field before Wednesday night's game and underwent another test Thursday.
Baker is hoping to return to Cincinnati on Friday. Bench coach Chris Speier ran the team for a second straight game.
Cueto (18-9) pitched six shutout innings as the Red completed a three-game sweep.
The Reds broke a scoreless tie by getting five straight singles off reliever Manuel Corpas (0-2) in the seventh during a five-run rally capped by Henry Rodriguez's two-run double.
Chicago starter Jason Berken allowed just two hits in six innings against a lineup missing most of the Reds' regulars.
Cueto gave up five hits with four walks and broke a three-game losing streak.
The Cubs scored in the seventh on Anthony Rizzo's RBI single and in the eighth on Welington Castillo's fifth homer again. Rizzo had an RBI grounder in the ninth against Alfredo Simon, who pitched the final 1 1-3 innings for his first save in as many chances.
The Reds secured their second playoff appearance in three years despite having the back of their bullpen wiped out by injuries during spring training and losing their best hitter - 2010 National League MVP Joey Votto - for nearly two months.
Baker did some of his best managing to pull them through.
His first challenge was cobbling together a bullpen after closer Ryan Madson tore an elbow ligament in spring training, ending his season. Setup men Nick Masset and Bill Bray also got hurt before the season opened.
Baker eased Aroldis Chapman into the closer's role, and the hard-throwing left-hander set a franchise record with 27 consecutive saves.
Baker also had to juggle his batting order and lineup after Votto tore knee cartilage and was sidelined on July 16. The Reds went on their best tear of the season without their top hitter, going 32-16 and taking control of the NL Central.
There was some good fortune, too. All five starters have made it through the season without injury, a franchise record. The Reds had to use a sixth starter only because of a doubleheader.
By the time September started, the Reds were firmly in control and counting down the days until they'd clinch.
NOTES: Cueto's two strikeouts gave him a career-best 159. ... Reds 2B Rodriguez and CF Denis Phipps made their first career starts and SS Didi Gregorius started for just the fourth time. ... The Cubs stay home to play the wild card-contending Cardinals with Chris Carpenter (0-0) set to make his season debut against Chris Volstad (3-10). ... The Reds will start Bronson Arroyo (12-8) at home against the Dodgers' Joe Blanton (9-13) on Friday night. ... Berken, picked up on waivers from Baltimore earlier this month, struck out four batters in one inning - the fifth Cubs pitcher to ever do that - when Ryan Hanigan reached on a third strike wild pitch in the second.
AP Sports Writer Joe Kay contributed to this report.