ST. LOUIS — Rookie Joe Ross had trouble gripping the ball in 89-degree heat. Casey Janssen paid dearly, again, for failing to hit his spots.
The Washington Nationals blew another late lead against St. Louis and they're just one game above .500 after Brandon Moss' three-run walk-off home run with two outs in the ninth inning gave the Cardinals an 8-5 win Tuesday night.
"These are two big losses and I had my hand in both of them," said Janssen (1-4), who has taken the loss both games. "Time isn't on our side."
The Nationals are 66-65 and missed a chance to gain a game on the New York Mets, who lead them by 6 1-2 games in the NL East.
"Oh man, that's one that hurts," said Bryce Harper, who had two hits, two walks and a sacrifice fly. "Definitely had a great team on the ropes."
The NL Central-leading Cardinals have won nine of 10 and lead the division by six games. They've won nine in a row over Washington, coming from behind the last two nights.
Moss, who struck out with the bases loaded to end the third, homered off Janssen to straightaway center on a 1-0 count. Janssen took the loss on Monday, allowing four runs in two-thirds of an inning.
"It was a cutter," Janssen said of the home run pitch. "I was trying to go in and I left it up and it was terrible."
Ross lasted just 2 2-3 innings, giving up one hit to go with a season-high six walks and was charged with three runs. Next time he faces conditions like this, he said he might just try the resin bag.
"The first two innings I guess were all right and the third inning I was just kind of sweaty and trying to wipe my hand off," Ross said. "My pants were kind of sweaty and then I was just having a tough time finding the zone."
Mitch Harris (2-1) worked the last two innings, allowing two hits.
Ryan Zimmerman homered and Anthony Rendon had a two-run double in a four-run third for Washington.
The Cardinals scored three runs on one hit in the bottom of the third and tied it with two runs on one hit with an error in the eighth against Drew Storen, who contributed with a wild throw to third going for the lead runner on Greg Garcia's sacrifice bunt.
Cardinals call-up Marco Gonzales also lasted 2 2-3 innings, allowing four runs on seven hits with lots of solid contact.
Gonzales, who was 1-4 with a 5.20 ERA for Triple-A Memphis, started in place of Carlos Martinez, who was scratched with back soreness but is expected to make his next turn.
Carlos Villanueva replaced Gonzales and restored order, allowing one hit in 3 1-3 innings with six strikeouts.
Nationals: Stephen Strasburg, limited to four innings by upper back tightness in his last start, played catch without problems. If he feels well, he'll be scheduled for a bullpen session that would keep him on track to go Friday against Atlanta.
Cardinals: Matt Holliday took batting practice at Busch Stadium for the first time since straining his right quadriceps muscle and lined several homers. Lefty Tim Cooney will be shut down after three weeks of inactivity following an appendectomy.
Max Scherzer (11-11, 2.88) tries to shake off a forgettable August in which he was 0-3 with a 6.43 ERA and surrendered seven homers in five starts. Michael Wacha seeks his 16th victory and was 3-0 with a 1.13 ERA in August. "We've got Maxie going for us," manager Matt Williams said. "Try to get that one and head back home."