ST. LOUIS -- Lance Lynn produced another quality start, leading to another win for the team with the best record in the major leagues.

Grinding his way through seven innings Monday night, Lynn helped the St. Louis Cardinals earn their eighth win in 10 games since the All-Star break with a 4-1 verdict over the Cincinnati Reds at Busch Stadium.

Second baseman Kolten Wong provided all the backing Lynn needed with a fourth-inning grand slam.

Lynn (8-5) gave up five hits and a run, walking three and striking out five in his 13th quality start out of 19 outings. He threw 115 pitches, the last one retiring All-Star third baseman Todd Frazier on a foulout to first with two runners on to end the seventh as Frazier slammed his bat in frustration.

Kevin Siegrist relieved and worked a 1-2-3 eighth, and closer Trevor Rosenthal picked up his 31st save with a clean ninth. St. Louis (64-35) upped its National League Central lead over the idle Pittsburgh Pirates to 6 1/2 games and improved to 37-13 at home.

Raisel Iglesias (1-3) was touched for six hits and four runs in six innings, walking none and fanning seven. He and Lynn combined to hit five batters, and plate umpire Marty Foster warned both benches in the sixth after Iglesias plunked center fielder Peter Bourjos for the second time.

Cincinnati (43-54) lost for the fourth time in five games, falling to 18-32 on the road.

The Reds opened the scoring in the top of the third on a sacrifice fly by right fielder Jay Bruce, plating second baseman Brandon Phillips. However, Cincinnati got just one run in the inning after filling the bases with no outs.

St. Louis loaded the bases in the fourth and cashed in when Wong belted the second grand slam of his career on a fat 3-2 fastball. The 11th homer of the year for Wong gave the Cardinals a 4-1 lead.

Cardinals catcher Yadier Molina departed the game for a pinch hitter, backup Tony Cruz, in the fifth. No reason was given for Molina's removal.

NOTES: St. Louis CF Randal Grichuk (groin) and 1B Mark Reynolds (hand) didn't play Monday, though they were available to pinch-hit. Grichuk was injured Sunday in the Cardinals' 3-2 loss to Atlanta, while Reynolds was drilled by a pitch Saturday night. ... Cincinnati recalled C Kyle Skipworth from Double-A Pensacola to take the roster spot of RHP Johnny Cueto, who was traded to Kansas City on Sunday. Skipworth was batting .237 with nine homers and 19 RBIs with the Blue Wahoos. ... The Cardinals activated RHP Mitch Harris (right groin) from the 15-day disabled list and optioned him to Triple-A Memphis.