ST. LOUIS -- Nolan Arenado made sure the Rockies didn't waste another scoring chance Monday night.
Opportunities went unfulfilled in the third and fourth innings against Cardinals starter Carlos Martinez. But with Martinez having left the game with a right shoulder strain with two outs in the fifth, Arenado parked a grand slam to center field off reliever Daniel Poncedeleon for a 4-0 lead. 
Despite Arenado's blast, the Cardinals would rally back for a 5-4 victory in 10 innings.
The slam -- the fifth of Arenado's career -- was his National League-leading 28th homer of the season. It put him three ahead of four other NL players -- the Brewers' Jesus Aguilar, the Cardinals' Matt Carpenter, the Nationals' Bryce Harper and the Dodgers' Manny Machado (who hit all but one of his homers with the Orioles in the American League).
"I'm trying to get a good pitch to hit, trying not to expand in that situation," Arenado said. "I'm still being me, still being aggressive, still being ready to hit. He made a mistake and I was able to hit it. That's all it was.
"I take a lot of pride in being able to drive runs in, and I was happy to do it right there."
The Rockies entered play Monday having won four straight. Arenado had homered in two of the games.
The Rockies had a runner at third with one out in the third, and runners at the corners with one out in the fourth, but couldn't score off Martinez, who struck out nine before leaving the game after 4 2/3 innings. Poncedeleon walked Ian Desmond, before serving up the homer on an 0-1 pitch -- a 95.8-mph fastball.
Arenado coming through in big situations is becoming a regular occurrence. He entered Monday's game with a .335 career batting average with runners in scoring position. According to Stats Inc., Arenado was fourth among all players since 1974 and second among active players. Those with higher averages in that situation are Hall of Famers Tony Gwynn and Rod Carew, followed by Reds star Joey Votto.