The Astros leaned on their starting pitching depth last postseason to make up for their shortcomings in the bullpen. Ever since 2017 ended, it's been a question of when -- not if -- Houston would make a big bullpen acquisition to bolster its chances at back-to-back championships.
Houston's big offseason move was to trade for starter Gerrit Cole, passing on the plethora of free-agent relief arms on the market. Now, with a number of quality relievers available via trade, the Astros find themselves without a true need for another bullpen piece despite a public perception that the unit needs another proven contributor.
With a 2.58 ERA, the Astros have the lowest bullpen mark in the American League. They don't have the same type of power arms that the Yankees do -- Houston's 'pen ranks 10th out of 15 in the AL in strikeouts -- but their .213 opponents' batting average is second to New York (.196), as is their .604 opponents' OPS, which sits just two points behind the Yankees' .602.
It's also worth noting that Houston hasn't had to rely on its bullpen as much as other teams thanks to a rotation that ranks first in the league in both ERA (2.95), innings pitched (536.1) and strikeouts (614) this season.
A source with knowledge of the Astros' thinking said Houston plans to gauge the market and pounce if there's value to be had, but GM Jeff Luhnow is unlikely to make a move simply for the sake of appearances.
"It's going to be really hard for them to upgrade given that adding someone means pushing a capable -- even good -- reliever like [Tony] Sipp, [Will] Harris or [Collin] McHugh off the playoff roster," the source said. "There's pressure to do something, but it doesn't really make sense."

One general manager concurred, wondering why Houston would be itching to make a move in the bullpen at all.
"They have six relievers that I would consider above average," the GM said. "So unless they are sending one of those guys back in a deal, it's hard to see the fit."
Another GM, however, believes that if the Astros can make a good bullpen even better, they should go for it.
"You can always upgrade, especially from the left side for them," the second GM said. "Pens are never good enough."
Adding a left-hander would be the logical move for the Astros, who currently have just one (Sipp) in the bullpen.
Sipp struggled so badly last season that he was left off the postseason roster, but the soon-to-be 35-year-old has rebounded this year, holding lefty hitters to a .114 average (4-for-35) and a .327 OPS.
Chris Devenski (.495 OPS) and Hector Rondon (.509 OPS) have also handled left-handers well, while McHugh (.341 OPS), Brad Peacock (.369 OPS) and Harris (.516 OPS) have dominated righties.

McHugh (0.97), Devenski (1.32) and Rondon (1.50) all have ERAs below 2.00, while Peacock (2.25) and Sipp (2.29) aren't far behind.
Joe Smith, who returned from the disabled list on Tuesday after missing the past four weeks, overcame a rocky April to pitch brilliantly in May and early June. He had a .097 opponents' batting average and had allowed just two runs in 12 outings (1.74 ERA) before landing on the DL with elbow inflammation.
If anything, the weak link statistically has been Ken Giles and his 4.08 ERA, though he is 11-for-11 in save opportunities and has a strikeout-to-walk ratio better than 9-to-1 this season. If anything, his October meltdown is the biggest drawback when it comes to Giles, who will surely be reminded of his postseason struggles when the playoffs begin.
Could Houston add a proven closer to handle the ninth inning? It's possible, but the Astros seem disinterested in trading either of their top two prospects, outfielder Kyle Tucker or right-hander Forrest Whitley, who rank No. 8 and 9, respectively, on MLB Pipeline's overall Top 100 prospects.
Come October, Justin Verlander, Cole and Charlie Morton seem to be locks for the playoff rotation, and although Dallas Keuchel has struggled at times this season, it's difficult to envision Houston not giving him a start. That would shift Lance McCullers to the bullpen, adding a hard-throwing arm to the relief corps.
"The bar to add a right-handed reliever is higher for them, but the litmus test is the player that makes them better," the source said. "They can do nothing and feel like they are one of the best teams going into the playoffs."
If Houston does decide to make a bold bullpen move in the coming weeks, here are five candidates to join the defending champions:
Zach Britton, LHP, Orioles
The most intriguing rental reliever on the market, Britton was one of the best bullpen arms in the game from 2014-16. He hasn't looked the same in nine appearances since returning from offseason Achilles surgery, though the Orioles are unlikely to deal the 30-year-old on the cheap. If Britton can regain his form before July 31, he has the potential to be a lock-down, game-changing acquisition. The Astros flirted with the idea of a trade for Britton last summer, too.
Adam Conley, LHP, Marlins
Conley's velocity has taken a big leap since he moved to the bullpen. His fastball is averaging 94.8 mph according to Statcast™ after clocking in at 89.7 mph in 2017. Conley has a 1.50 ERA this season, pitching effectively against both lefties (.515 OPS) and righties (.546 OPS). Miami is drawing interest in several relievers, including right-handers Kyle Barraclough and Drew Steckenrider, but the left-handed Conley seems to make the most sense of the three for Houston.

Brad Hand, LHP, Padres
Although Sipp is the only Astros reliever eligible for free agency at the end of the season, adding a quality arm of Hand's level who is under club control through 2021 at a reasonable cost ($6.5 million in 2019, $7 million in 2020, $10 million option in 2021) would make sense for a team expecting to contend for the next few years. It's tough to imagine Houston landing Hand without giving up one of its top prospects, but three-plus years of control might make the price easier to handle.

Raisel Iglesias, RHP, Reds
Like Hand, Iglesias comes with multiple years of club control, as the Reds closer is in the fifth year of his seven-year, $27 million deal. Iglesias is set to earn $5 million in each of the next two seasons, a team-friendly number for one of the league's top closers, though Cincinnati is unlikely to deal Iglesias unless the price is right. While Iglesias dominates righties (.141 average, .455 OPS), he's susceptible to lefties, who have hit four homers against him in 66 at-bats this season.

Blake Treinen, RHP, Athletics
Following a trade last summer from the Nationals, Treinen has rejuvenated his career in Oakland. Treinen is 21-of-23 in save opportunities this year, successfully converting his past 20 chances. The 30-year-old right-hander has owned righty hitters to the tune of a .117 average and .382 OPS, while posting respectable numbers against lefties (.225 average, .534 OPS). Treinen is making only $2.15 million this season and is arbitration eligible for two more seasons, making him another intriguing, controllable option, though the return would be costly.