Monday night, the Houston Astros open a crucial three-game series with the second-place Athletics. Houston has a 6 1/2-game lead in the AL West, and this series will determine whether the team runs away with the division, or whether we get a genuine division race down the stretch. It's an important series, for sure.

This week's series will not, however, determine whether the Astros buy or sell at the deadline. They have the fourth best record in baseball at 64-37 -- SportsLine puts their postseason odds at 99.1 percent -- and their championship window is wide open. The Astros are buying. There is zero doubt about that.

Rotation help figures to be Houston's top priority prior to the single July 31 trade deadline. Their rotation depth chart currently looks something like this:

  1. RHP Justin Verlander
  2. RHP Gerrit Cole
  3. RHP Wade Miley
  4. RHP Lance McCullers (rehabbing from Tommy John surgery)
  5. RHP Brad Peacock (out until mid August with shoulder issue)
  6. RHP Corbin Martin (rehabbing from Tommy John surgery)
  7. RHP Rogelio Armenteros
  8. RHP Jose Urquidy
  9. LHP Framber Valdez

The Astros are so short on rotation depth right now that over the weekend manager A.J. Hinch told reporters, including Chandler Rome of the Houston Chronicle, that the team will use a four-man rotation until the trade deadline. They're going to take advantage of scheduled off-days to avoid using a fifth starter as long as possible.

Verlander, Cole, and Miley form a heck of a top three to take into the postseason, but remember, the Astros need rotation help beyond this year. Cole, Miley, and Collin McHugh will be free agents after this season, Martin will miss all of next year, and McCullers could miss the start of the season. Adding a pitcher with control beyond 2019 would be the ideal scenario.

Also, the Astros could pursue a left-handed reliever before the July 31 trade deadline. They have an all right-handed bullpen at the moment and, come October, having a left-on-left matchup specialist to face hitters like Max Kepler, Eddie Rosario, Didi Gregorius, Matt Olson, Austin Meadows, and others wouldn't be a bad idea.

With the trade deadline rapidly approaching, we here are CBS Sports are going to rank the top 10 trade targets for various contending teams priority to July 31. We've already covered the Yankees, Dodgers, and Cubs. Now here are the 10 best fits for the Astros leading up to the trade deadline.

2019 MLB Trade Deadline: Top 10 Astros trade targets
1
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Marcus Stroman Toronto Blue Jays SP

Key stat: 57.1 percent ground ball rate (second highest in baseball)

According to MLB Network's Peter Gammons, the Astros were heavy on Blue Jays righty Marcus Stroman two years ago, before they pulled the trigger on the Verlander trade. That interest reportedly remains and it makes sense. Stroman is very good, he has the spin rates the Astros love, and he will remain under team control through 2020 as an arbitration-eligible player. He fits what Houston needs now and what they need after this season. Stro's a great fit for the 'Stros.

2
Robbie Ray Arizona Diamondbacks SP

Key stat: 30.6 percent strikeout rate since 2016 (third highest in baseball)

Like Stroman, Diamondbacks lefty Robbie Ray is under team control as an arbitration-eligible player in 2020, and the Astros do have interest in acquiring him. MLB.com's Jon Morosi says Houston has Ray on its radar. High strikeout, high velocity lefties will always be in demand, and if the Astros can help Ray add spin to his fastball a la Cole, he could become one of the game's truly elite starters in a hurry. For now, his elite strikeout rate and team control in 2020 is enough to make him a good target.

3
Madison Bumgarner San Francisco Giants SP

Key stat: 3.14 ERA since June 1

Although the Astros are on Madison Bumgarner's 10-team no-trade list, I have to think the Giants southpaw would be open to joining a World Series contender for the stretch run. Bumgarner is an impending free agent, so he won't fix Houston's rotation issues beyond this year, but gosh, imagine going into a postseason series with Verlander, Cole, and Bumgarner lined up to start the first three games? Ken Rosenthal of The Athletic recently reported the Astros do have interest in MadBum.

4
Matthew Boyd Detroit Tigers SP

Key stat: 32.2 percent strikeout rate (fourth highest in baseball)

Not surprisingly, the Astros also have interest in Tigers southpaw Matthew Boyd, reports MLB.com's Jon Morosi. Boyd has the strikeout and spin rates they love, and he is under team control another three years beyond 2019. The question is price. Morosi says Houston won't trade top outfield prospect Kyle Tucker for Boyd, and the Tigers are known to stick to their guns with their top trade chips. Asking price may be an obstacle, which is why Boyd doesn't rank higher on this list.

5
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Will Smith San Francisco Giants RP

Key stat: 52.1 percent strikeout rate vs. lefty batters (highest in baseball among lefties)

The Astros could use a shutdown lefty reliever and I'm not sure a better one will get traded at the deadline than Giants southpaw Will Smith. He has annihilated lefties this year -- Smith owns a 25/1 K/BB in 48 plate appearances against lefties -- and he's really good against righties too. Smith is an overqualified left-on-left matchup guy. He's a rental, but boy, what a rental he is. Smith and Ryan Pressly would make a formidable setup duo in front of closer Roberto Osuna.

6
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Noah Syndergaard New York Mets SP

Key stat: 97.8 mph average fastball velocity (highest in baseball among starters)

This has been a very odd year for Mets righty Noah Syndergaard. He still has maybe the best power arsenal in the game -- weirdly, Syndergaard's velocity is great but his spin rates are underwhelming -- but is more hittable than you'd expect. With two years of control remaining, my guess is the Astros would happily take the 26-year-old Syndergaard and see whether they can make him better a la Cole. MLB.com's Jon Morosi reports Houston indeed has interest in Syndergaard.

7
Mike Minor Texas Rangers SP

Key stat: 2,644 rpm average fastball spin rate (highest in baseball among lefties)

Few pitchers in baseball check as many analytical boxes as Rangers ace Mike Minor. He has elite spin rates on his fastball and slider, and I don't think any team in baseball knows what to do with elite spin rates better than the Astros. Also, Minor is signed through next season, so he's not a rental. Would the Rangers and Astros get together to make an intra-division trade? I suppose it depends on the price. Texas would be foolish to say no if Houston makes the best offer.

8
Zack Wheeler New York Mets SP

Key stat: 2 possible starts before the trade deadline

In a weird way, Zack Wheeler's shoulder injury could make him more desirable for the Astros. The injury will inevitably knock the price down, and his velocity and spin rates are right up Houston's alley. Buying low on a potential impact starter -- it's not hard to envision the Astros helping Wheeler take his game to the next level -- would be a very Astros move. Wheeler is an impending free agent, so he won't help next year, but helping this year is good enough.

9
Jake Diekman Kansas City Royals RP

Key stat: 33.2 percent strikeout rate (eighth highest among lefty relievers)

The surface numbers aren't great. Lefties are hitting .217 against Royals southpaw Jake Diekman this year, though they have as many walks and hit-by-pitches (11) as strikeouts (11), leading to a .368 on-base percentage. That's not good for a potential left-on-left matchup guy. That said, Diekman throws very hard and has a knockout slider. At the right price, he can be someone the Astros bet on to be their postseason matchup lefty. You have to squint a bit, but the fit is there.

10
Tony Watson San Francisco Giants RP

Key stat: 87.0 mph average exit velocity allowed (20th best among lefties)

Tony Watson's numbers against lefty batters are shockingly bad: .333/.348/.467. That said, the Giants southpaw has thrown exactly 10 innings against lefties this year, so it's not a big sample at all, and it doesn't line up with the rest of his career (Watson held lefties to a .231/.252/.317 line last season). Will Smith he is not, but Watson is a solid enough left-on-left matchup reliever. His contract includes an affordable $2.5 million player option for 2020 as well, so he might stick around beyond this year.