ST. LOUIS -- The maturation of Carlos Martinez continues.

Overcoming two rain delays that lasted nearly 2 1/2 hours and an opponent that torched him for nine hits and seven runs the last time it faced him, Martinez turned in a strong performance Sunday night as the St. Louis Cardinals polished off a sweep of the Chicago Cubs with a 4-1 win.

Martinez (9-3) checked Chicago on two hits and a run over six innings, walking three and fanning six. He lowered his ERA to 2.80.

"It was a good test for him, no question," St. Louis manager Mike Matheny said of Martinez's ability to remain on point despite the delays. "He always wants to do more, go out there and fire. It was tough with the long delay, but he stayed focused."

After waiting 46 minutes to toss the first pitch as threatening weather danced around Busch Stadium but didn't deliver on its promise, Martinez made it through two innings. Then torrential downpours halted the proceedings for 1 hour, 43 minutes, with tornado warnings issued for downtown after a twister touched down about 30 miles west of the ballpark.

Martinez kept loose by frequently throwing in the batting cage underneath the ballpark.

"Every five minutes, I'd go to the cage to throw and be ready," he said through an interpreter. "I told (pitching coach Derek Lilliquist) I'd be ready when the game resumes. Even though the rain stopped the game, I stayed focused on doing my job."

Aiding Martinez's cause was that the Cardinals didn't have a long reliever available. Carlos Villanueva mopped up the last three innings Saturday night in an 8-1 win or he might have taken over for Martinez.

Instead, Martinez remained in the game, and other than allowing a sacrifice fly to first baseman Anthony Rizzo in the third, he shut the Cubs down. Martinez demonstrated better command of his off-speed pitches after the second delay while mixing in fastballs clocked as high at 97 mph.

"When I got back, I felt comfortable," Martinez said. "I figured out how to use my (off-speed) pitches. I was pitching low in the (strike) zone."

Matheny hooked Martinez after 84 pitches, and the bullpen wrapped it up with three scoreless innings. Closer Trevor Rosenthal worked around two ninth-inning singles to notch his 23rd save in 24 chances.

The outcome improved St. Louis' majors-best record to 51-24 and upped its National League Central lead over the second-place Pittsburgh Pirates, who lost 2-1 to the Atlanta Braves, to nine games. The Cardinals also won for the 29th time in 36 home games.

Jason Hammel (5-3) matched Martinez until the fourth, when St. Louis thumped three doubles that scored two runs and broke a 1-1 tie. Right fielder Jason Heyward and catcher Yadier Molina each knocked in a row.

Hammel departed after allowing a leadoff double to second baseman Kolten Wong in the fifth. Reliever James Russell promptly coughed up a run-scoring double to third baseman Matt Carpenter to cap the scoring.

"Every team knows if you do the small things, you have a chance to win," Hammel said. "I have to do better at pitching."

The veteran right-hander was charged with six hits and four runs in four-plus innings. He walked one and whiffed seven.

Chicago (39-35) sustained its fifth consecutive loss and dropped 11 1/2 games off the Cardinals' blistering pace in the division.

Molina had two of the Cardinals' six doubles, their highest total in a game since they collected six last June in Colorado. First baseman Xavier Scruggs added an RBI single in the second, his ninth hit in 16 at-bats since being recalled June 19 from Triple-A Memphis.

However, the story was Martinez's ability to handle obstacles out of his control and turn in another good effort.

"You've got to have a routine for every situation," Matheny said. "He showed he was ready."

NOTES: Chicago placed LHP Tsuyoshi Wada (inflamed left deltoid) on the 15-day disabled list retroactive to June 23. Wada, who left his June 22 start against the Los Angeles Dodgers in the third inning, is 1-1 with a 3.73 ERA in seven starts. ... To replace Wada, the Cubs activated RHP Neil Ramirez (right shoulder inflammation) following a rehab stint. Ramirez had been out since April 16. He threw a scoreless inning Sunday night. ... St. Louis LHP Jaime Garcia (groin cramp) was able to throw his side session Sunday, and he could return to the rotation Thursday night against the San Diego Padres. Garcia was scheduled to start Tuesday night, but the team is skipping him in favor of RHP Lance Lynn.