CHICAGO -- The Chicago Cubs had a successful start in Friday's opener of their critical three-game series with the St. Louis Cardinals.

Now the Cubs hope there's not a price attached.

Friday's 8-2 victory opened a four-game lead over the Cardinals but not before their starting pitcher and catcher were ejected and shortstop Javier Baez suffered a medical scare that required attention after a diving play late in the game.

Whether suspensions are coming for right-hander John Lackey and catcher Willson Contreras after angry fifth-inning outbursts remains to be seen.

"I'm just happy because the team was able to come back and win the game," Contreras said. "I don't have any concerns on my part (about a suspension). If something happens, I'm going to take it like a man."

Baez, meanwhile, at least initially appeared to be OK and remained in Friday's game.

Kris Bryant went 3-for-4, including his 27th home run in the fourth inning while his teammates collectively used a seven-run sixth inning to take command.

The victory was the Cubs' fourth straight as Chicago (81-66) extended its NL Central lead to four games over the Cardinals with 15 to play. St. Louis (77-70) dropped its second in three games.

"These next 10 games are going to be important, so it's good to get off to a good start," Bryant said. "Obviously we started off not so good but we came alive there and that's all we needed."

Winning pitcher Carl Edwards Jr. (4-4) worked a scoreless sixth inning for the victory in place of right-handed starter John Lackey, who was ejected in the fifth after arguing home-plate calls.

Cardinals starter Carlos Martinez (11-11) took the loss after giving up seven runs, most coming late in a 5 1/3-inning outing.

"He had really good stuff today from the start, one of the best he had in the first inning as far as everything clicking," said St. Louis manager Mike Matheny. "That last inning there it kind of snowballed on him there but up until then he did a real nice job."

Jon Jay had two hits for the Cubs while Stephen Piscotty recorded a pair for the Cardinals.

Tommy Pham gave the Cardinals an early 1-0 lead with his 21st homer of the season. The one-out shot to left came on a first pitch off Lackey in the opening inning.

After Chicago piled up 39 runs, including 14 on Thursday, in this week's three-game sweep of the New York Mets, Martinez retired 10 straight Cubs until the fourth inning.

Bryant ended the shutout with his 27th homer, a one-out solo shot to center field to forge a 1-1 tie.

Martinez then walked Anthony Rizzo and gave up a base hit to Contreras. After Kyle Schwarber popped up to third, Jay followed with a looping single to left as Rizzo sprinted home.

Rizzo overran home plate, however, and was out as Pham threw to catcher Yadier Molina for the inning-ending out.

Martinez helped his cause with a run-scoring single to right-center moments after home plate umpire Jordan Baker called a ball on an apparent third strike. Kolten Wong came home for a 2-1 Cardinals lead.

Lackey and Contreras, meanwhile, both erupted in anger over the call and result, leading to the ejection of both as the Cubs traded 2-1 at that point. Contreras threw his mask and it apparently hit Baker.

"(Baker) had no argument back," said Lackey. "He was just trying to say 'that's enough.' Usually when they do that they know they missed it. ... It's a pretty big spot there, it cost me a big league win. Those things don't grow on trees."

The pair were replaced by left-hander Justin Wilson and catcher Alex Avila. Wilson struck out Matt Carpenter to end the inning.

Lackey allowed two runs on three hits in his shortened 4 2/3-inning outing. He struck out four and walked two while throwing 74 pitches.

Chicago's big sixth inning chased both Martinez and reliever Matt Bowman.

The Cubs had two runners on and none out when Avila singled home Bryant to force a 2-2 tie. Jay came up with one gone and drove in Rizzo with a base hit for a 3-2 advantage.

Martinez waked Jason Heyward to load the bases and then bobbled a fielder's choice grounder by Javier Baez as Avila scored.

That was all for Martinez, who departed with two runners on bases for Bowman.

Bowman gave up a two-run single to Ian Happ, scoring Jay and Heyward. Zobrist's sacrifice fly to center brought home Baez while Bryant's single to left-center delivered Happ for an 8-2 lead.

Martinez gave up seven runs on six hits while striking out five.

NOTES: St. Louis 2B Kolten Wong left Friday's game in the bottom of the fifth with lower back tightness. ... Following Friday's outing, Cardinals RHP Carlos Martinez is now two away from making 100 career starts. ... SS Paul DeJong's next homer will give him 23, good for second all-time among rookies in Cardinals single-season history. ... The Cardinals send RHP Michael Wacha (12-7, 3.99 ERA) against Cubs RHP Kyle Hendricks (6-5, 3.35) in Saturday's middle game. ... The Cubs have scored 754 runs, second only to Washington 755 atop the National League. ... Ten of Chicago's final 15 regular season games are against teams .500 or better. A total of 13 are against NL Central foes, a run broken by a two-game series at Tampa Bay on Sept. 19-20.