The Pittsburgh Pirates are stumbling on the road of late and cannot afford to continue that trend Tuesday in the opener of a three-game series versus the rival St. Louis Cardinals at Busch Stadium.

The Pirates opened their road trip by getting swept in three games at Colorado and their lead atop the NL Central is down to three games ahead of St. Louis. In Sunday's 3-2 loss to the Rockies, Pirates reliever Bryan Morris allowed the go-ahead run in the seventh inning to take the loss.

"We pack it up and we go," Pittsburgh manager Clint Hurdle said of the loss. "You honestly self-evaluate and move on and get ready to play in St. Louis."

Jeff Locke started for Pittsburgh and did not figure into the decision after he permitted two runs -- one earned -- in 5 2/3 innings. Locke entered the game with an MLB-best 1.83 ERA on the road.

Pedro Alvarez homered and Andrew McCutchen collected two hits and an RBI for the Pirates, who have lost four in a row and six of their last seven road contests. Six of the seven games during the stretch have been decided by two runs or less.

The Pirates are expected to unveil slugging prospect Andrew Lambo on Tuesday and he has split the 2013 season between Double-A Altoona and Triple-A Indianapolis. In 59 games this season for the Indians, Lambo has hit 17 homers with 51 RBI.

Pittsburgh's current slide comes on the heels of a five-game winning and the club hopes Charlie Morton can stick a pin in the losing streak when he toes the rubber Tuesday.

Morton has won three of his last four starts and the Pirates are 4-1 in his previous five trips to the mound. In a 4-2 win over Miami last Wednesday, Morton fanned five batters, did not allow a walk and yielded a pair of runs in seven innings. He is 4-3 in 10 starts with a 3.88 earned run average.

The righty recently lost to the Cardinals on Aug. 1 in a 13-0 defeat, charged with five runs and 10 hits in six innings, and is 2-8 with a 6.30 ERA in 12 career starts against them.

St. Louis will open the back stretch of its 10-game homestand (2-5) Tuesday night and salvaged the finale of a three-game series against the Chicago Cubs with Sunday's 8-4 win.

The Cardinals broke a 4-4 tie by scoring the last four runs of the game and sealed it with a two-run bottom of the eighth inning. Allen Craig had three hits, an RBI and two runs scored, Matt Carpenter went 3-for-5 with an RBI and scored twice and both David Freese and Jon Jay drove in a pair of runs.

"I thought the guys did a real good job of situational hitting, getting the runs in when they had money on the table," Cardinals manager Mike Matheny said after St. Louis ended a four-game slide.

The Cardinals gave Joe Kelly an early lead, but after he allowed four runs -- three earned -- in 5 1/3 innings, he received a no-decision. Randy Choate got the win after recording the last out in the sixth. Edward Mujica was called on for the final two innings and he kept the Cubs off the board for his 31st save.

Cardinals outfielder Carlos Beltran left Sunday's game in the fifth inning after he fouled a ball off his right foot. The All-Star suffered a contusion and X-rays were negative. Beltran is listed as day-to-day and is batting .305 with 20 homers and 62 RBI this season.

Adam Wainwright will make the start for the Cards Tuesday and he is 0-2 in his last three appearances. Wainwright previously pitched in last Monday's 3-2 loss against the Dodgers and was reached for three runs in seven innings, falling to 13-7 in 20 starts with a 2.66 ERA.

Wainwright, who has lasted at least seven innings in four straight outings, is 5-5 in 10 starts at Busch Stadium this season and 8-4 with a 5.19 ERA in 20 career matchups (16 starts) with the Pirates.

The Pirates have won seven of 10 contest against St. Louis this season and had a six-game winning streak in this series broken on Aug. 1. Pittsburgh is 30-18 against teams from the NL Central this season.