(SportsNetwork.com) - The MLB-best St. Louis Cardinals may have lost the last time out, but can add another series victory under their belt Sunday in the rubber match of a three-game set against the Pittsburgh Pirates.

The Cardinals are 8-0-1 in series action this season and sustained a 7-5 loss to the Pirates Saturday at PNC Park, where their 5-4 lead evaporated in the bottom of the sixth inning.

Jordy Mercer had a two-run double and Francisco Cervelli scored on a sacrifice fly to put the hosts ahead for good. Cardinals starter Carlos Martinez gave up all seven runs in 5 1/3 innings, walked four and struck out seven.

"He had a lot of positives to build on today," Cardinals manager Mike Matheny said of Martinez. "I think we saw some things in his mechanics, but those are hard to fix in the middle of a game."

Yadier Molina drove in two runs, Matt Holliday had three hits and both Jhonny Peralta and Jason Heyward recorded two hits, an RBI and a run scored for the Cardinals, who had won 10 of their previous 11 games.

St. Louis will visit the Cleveland Indians next for three games. It is playing this series without third baseman Matt Carpenter, one of the team's offensive leaders, because of "extreme fatigue."

Tyler Lyons will make another spot start for St. Louis' banged-up rotation Sunday and sports a 6.23 earned run average after just one appearance. Lyons, who pitched in 11 games (4 starts) last season, did not record a decision in Tuesday's 7-4 win over the Cubs, charged with four runs -- three earned -- in 4 1/3 innings.

Lyons, a left-hander, is 0-2 with a 4.20 ERA in three career meetings (2 starts) with the Pirates.

Pittsburgh has won two of three games following a five-game slide and needed a big rally in the sixth to cool off the rival Cards. Neil Walker homered and Mercer collected three RBI for the Pirates.

"We had some guys who were able to get something done and we were able to dig this game out of the dirt," Pirates manager Clint Hurdle said.

Vance Worley drew the start for the Buccos and did not record a decision with five runs and nine hits across five innings. Rob Scahill pitched a scoreless sixth inning for the win and Mark Melancon later notched his sixth save.

Pittsburgh turned a triple play in the second inning after Walker jumped to snare Molina's line drive at second base. Runners were caught off base at third and second for Pittsburgh's first triple play since last Sept. 14 against the Chicago Cubs.

It was the first 4-5-4 triple play in MLB history.

Pirates left fielder Starling Marte left the game after three innings with what the team called "severe dizziness." Sean Rodriguez took over in left field and went 1-for-2 with a run scored.

"We'll monitor him through the night and see how he shows up (on Sunday), and where we take it," Hurdle said of Marte.

The Buccos have scored 19 runs in their last three games and will start a seven-game road trip against Philadelphia and Chicago (Cubs) next.

The Pirates turn to Jeff Locke Sunday and he has a 2-2 mark in five starts to go along with a 4.85 earned run average. Locke has dropped back-to-back starts after going 2-0 in his first three outings and gave up four runs in seven innings of a 7-1 loss to Cincinnati on Tuesday.

Locke permitted six runs (5 earned) and eight hits in just 3 2/3 frames of a 6-2 loss against the Cubs on April 28. The left-hander has faced the Cardinals five times in his career and is 2-2 with a 3.76 ERA.

Pittsburgh was swept in three games at St. Louis from May 1-3.