The Pittsburgh Pirates (87-56) and Chicago Cubs (82-61) squared off earlier today in the first game of their Tuesday doubleheader. The second matchup will take place tonight at 7:05 p.m. ET at PNC Park and will feature the best pitching matchup of the four-game series.

Scroll to the bottom for the MLB live stream and radio broadcast.

Jon Lester (9-10, 3.50 ERA) will take the mound for the Cubs and face Pirates' left-hander J.A. Happ (5-1, 1.79 ERA) in a crucial contest for both clubs. Pittsburgh trails the St. Louis Cardinals by 2.5 games in the NL Central and is looking to earn its first division title since 1992.

On the other hand, Chicago trails the Cardinals by 6.5 games in the division, but holds a comfortable seven-game lead in the NL wild-card race over the San Francisco Giants. However, the Cubs have 10 remaining games against the MLB's best (Pirates, Cardinals and Royals) while the Giants will face the Reds, Diamondbacks, Padres, A's and Rockies in 14 of their remaining 18 games.

Chicago cannot afford to drop many more games, especially after losing two in a row to the Philadelphia Phillies over the weekend.

And that's where Lester comes in.

Since the beginning of July the left-hander has returned to form, going 5-4 with a 2.75 ERA and 90 strikeouts in 13 starts. In two career starts against Pittsburgh, Lester is 1-1 with a 2.08 ERA, 1.46 WHIP and 12 strikeouts in 13 innings. He defeated the Buccos earlier this year at Wrigley Field and tossed seven innings of one-run ball in the 4-1 victory.

However, the Pirates are on a roll. Manager Clint Hurdle's club has won three consecutive series against NL Central opponents and scored 57 runs in those 10 games. Additionally, Happ has won his last five consecutive starts and the team has won six of the seven games he has pitched since the left-hander was acquired from the Seattle Mariners at the trade deadline.

His only loss with Pittsburgh came against the Cubs at PNC Park back on Aug. 4. The veteran surrendered four earned runs on nine hits and two walks over 4 1/3 innings in the 5-0 defeat. His five career starts against Chicago also haven't gone well - he's 1-3 with a 6.04 ERA and 2.01 WHIP in 25 1/3 innings.

The Cubs were on a good run until the Phillies outmatched them on offense on Saturday and Sunday. They've had no trouble scoring runs in the month of September, having notched 72 in 12 games before today's doubleheader.

The next three games of this series could determine the balance of power in the NL Central heading into the final two weeks of the season.

Click here for the each team's lineups.

Check out the live stream for tonight's game here as well as the live radio broadcast here (PIT) or here (CHC).