Should the Washington Nationals franchise make the postseason for the first time since 1981, right-hander Stephen Strasburg isn't expected to pitch for the club due to an innings limit.

The Nats, though, aren't putting the cart before the horse and they'll turn to Strasburg on Sunday afternoon for the finale of a four-game series against a potential playoff opponent in the St. Louis Cardinals.

Washington stated before the season that Strasburg would be on an innings limit this year after he underwent Tommy John surgery late in 2010. The 24- year-old is approaching that mark, having thrown 150 1/3 frames through 26 outings.

It is unknown when exactly Strasburg will be shut down, though he is likely down to his last two or three outings.

The top pick of the 2009 draft was aiming for a fifth straight win on Tuesday at the Miami Marlins, but was instead handed a 9-0 loss. He was charged with a career-high seven runs -- five earned -- on nine hits over five innings and struck out just three.

"I struggled for pretty much the whole game. It's a learning experience for me," said Strasburg, who fell to 15-6 with a 3.05 earned run average this season and faces the Cardinals for the first time in his career.

Strasburg will try to secure a series victory today after Washington dropped a 10-9 slugfest to St. Louis on Saturday. While the Nats were denied a fourth straight win, the Cardinals halted a four-game slide, one in which they had been limited to just one run while getting shut out three times.

The Cards moved to 4-5 on a tough 10-game road trip that went through first- place Cincinnati, Pittsburgh and Washington.

Carlos Beltran tied the game with a pinch-hit RBI single in the eighth inning before David Freese drove in the go-ahead runner in the ninth inning as St. Louis snapped a seven-game slide in the nation's capital.

Freese and Matt Holliday both hit two-run homers and Matt Carpenter added a three-run double for the Cardinals, who are 1 1/2 games ahead of the Pittsburgh Pirates for the NL's second wild card spot.

"Our guys have the ability to put runs on, no matter who we're facing," said Cardinals manager Mike Matheny.

Adam LaRoche knocked in three runs for the NL East-leading Nationals, who maintained a 6 1/2-game edge over the second-place Atlanta Braves.

"We've got a chance to win the series (Sunday). We have been playing good ball," said Nats outfielder Jayson Werth.

Cardinals starter Kyle Lohse and his Washington counterpart, Jordan Zimmermann, were both tagged for eight runs. Only five of the runs Lohse allowed were earned.

Getting the call for St. Louis is Jake Westbrook, who has split his last two decisions despite giving up 12 runs over a pair of five-inning outings.

After escaping with a win over the Houston Astros, Westbrook allowed seven runs, 11 hits and four walks in a 9-0 setback to the Pirates on Tuesday. He fell to 13-10 with a 3.94 ERA in 26 games this season.

The 34-year-old righty also dipped below .500 on the road at 5-6 with a 3.92 ERA in 12 games. He'll look to even his career mark against the Nats as well as he faces them for the first time in 2012 having gone 1-2 with a 6.23 ERA against them in three previous encounters.

Washington was 4-2 versus St. Louis last season.