The Houston Astros (76-66) are perhaps facing their toughest test of the 2015 MLB season. Tonight they will begin the end of their 10-game road trip with a four-game series against the Texas Rangers (75-67) at 8:05 p.m. ET.

And Monday night's matchup is MLB.TV's Free Game of the Day. Click the link for the live stream.

In a battle of left-handers, the Rangers will send Cole Hamels (9-8, 3.76 ERA) to the hill to face the Astros' Scott Kazmir (7-10, 2.63 ERA). Houston leads Texas by 1.5 games in the AL West thanks to the Astros' recent slide (6-9 in their past 15 games).

However, the Astros are riding a crucial wave of momentum after a huge ninth-inning comeback on Sunday against the Los Angeles Angels. Houston was trailing 3-0 in the top of the ninth and managed to score five runs behind Jed Lowrie's pinch-hit three-run homer and avoid the sweep. It was a much-needed victory, considering the Astros were just 1-4 on their road trip entering yesterday's matchup.

Tonight they'll get a crack at Hamels, who is 4-3 with a 4.90 ERA and 1.26 WHIP in 10 career starts against Houston. The Rangers acquired Hamels before the non-waiver trade deadline and the left-hander has been working on his transition to the American League.

Hamels surrendered 12 earned runs in his first three starts, but has since settled and gone 3-0 with a 3.21 ERA and 23 strikeouts in his last four outings.

As for Kazmir, the left-hander was acquired from the Oakland Athletics before the non-waiver deadline. He hasn't had much of a change of scenery, considering he's still pitching in the AL West and is now in his hometown of Houston, but he's been a bit inconsistent in his past five starts.

Kazmir is 1-3 with a 5.02 ERA over that span. He has also lost his last four road starts.

He faced Texas earlier in the year, but was handed a loss after giving up four runs (one earned) on six hits and two walks in 5 2/3 innings. However, he's been much more successful against the Rangers throughout his career, having gone 11-6 with a 2.92 ERA and 1.15 WHIP in 22 starts. 

These two clubs boast top-10 offenses, so Hamels and Kazmir will have their hands full as yet another crucial division series will take place in September.

Click here for the lineups.

Check out the live stream for tonight's matchup here as well as the live radio broadcast here (TEX) or here (HOU).