The Seattle Mariners and Houston Astros will begin a three-game series on Monday night. It's time to continue our MLB odds series and make a Mariners-Astros prediction and pick.

This is one of the most important series of the year for the Mariners. They are currently in second place in the AL West, trailing the first-place Astros by just 4.5 games. This series is one of the best chances to make up ground, so they need to capitalize on it and take at least two of three against their rival.

The Astros will play to defend their division lead, so this series also presents a huge opportunity for them. Beating the Mariners could secure Houston's first-place finish, so there's plenty at stake here.

Here's how the bookmakers have set the lines for Monday's game.

MLB Odds: Mariners-Astros Odds

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Seattle Mariners +1 1/2 (-123)

Houston Astros -1 1/2 (+103)

Over 8 1/2 runs (-117)

Under 8 1/2 runs (-103)

Why The Mariners Could Cover The Spread

Seattle has leaned on its pitching staff to secure wins throughout the year, and Monday's game is no different. The Mariners are set to send out pitcher Yusei Kikuchi to make the start in this crucial game. Kikuchi has been solid for most of the season, earning himself a 4.12 ERA and a 1.23 WHIP. Those are pretty decent numbers, and they get even better when Kikuchi pitches on the road. The lefty owns a 3.86 ERA on the road, a number that jumps to 4.38 when Kikuchi plays at home. Another factor that favors Kikuchi is Houston's offensive numbers at home. The Astros are actually slightly worse at the plate when they play at Minute Maid Park, posting a lower batting average and OPS at home.

The Mariners aren't known as a great offensive squad, but they have shown improvements in recent games. They've scored 24 runs over their last three contests, with all three games ending in Seattle victories. This lineup has also earned a .241 batting average throughout September. Despite their struggles throughout the year, this Mariners team is putting things together at the right time. They won't be an easy out in a game that could play a huge part in deciding their postseason hopes.

Why The Astros Could Cover The Spread

Unlike the Mariners, Houston hasn't gone through any offensive struggles this season. The Astros rank inside the top three in MLB in batting average, slugging percentage, OBP, and OBP. This lineup has also faced Kikuchi several times this season, earning themselves great results. Houston has hit against Kikuchi for a total of 14 innings, scoring 10 runs in that span. The Astros have shown the ability to get to Kikuchi throughout the year, and that shouldn't change in this game.

Houston starter Lance McCullers Jr. is set to make the start in Monday's game. McCullers has been fantastic all year long, posting a 3.20 ERA and a 1.25 WHIP on the season. Those are great numbers, and they've held up against this Mariners lineup multiple times this season. The righty has faced Seattle three times this season, pitching 17 innings while only giving up six runs. The Mariners should present a bit more of a challenge this time out, but McCullers should be up to it.

Final Mariners-Astros Prediction & Pick

The over looks like a solid play here, but it's a little too risky for a confident bet. Taking the Astros to cover is a much safer pick, as they have plenty of advantages in this series opener. The Mariners have been terrible against McCullers in the past, while the opposite can be said about these Astros hitters and Kikuchi. Houston may need all nine innings to make it happen, but the cover should happen.

FINAL PICK: Houston Astros -1 1/2 (+103)