The Houston Astros did exactly what they had to do in the series opener against the Miami Marlins on Monday night at Daikin Park with a massive 8-5 win. The offensive firepower returned after a quiet three-game stretch against the Baltimore Orioles, and it came at such a crucial time. After a disappointing sweep suffered at the hands of the Orioles this past weekend, this Marlins series is so important for the Astros to get back on track and stay close in the postseason picture. Jeremy Peña hit a grand slam and Yordan Alvarez crushed two homers of his own on Monday.It's time for the Astros to build upon that. “It was a tough series that we just played,” Peña said after Monday's win, according to Brian McTaggart of MLB.com. “We flushed that and we showed up today to win a game and we’ll keep going with the momentum and show up tomorrow and try to win another game. Hopefully this snowballs and we keep going.”Here's the lineup for game two against the Marlins and a chance for the Astros to take a much-needed series win. Astros Lineup for July 21 vs MarlinsHouston Astros designated hitter Jose Altuve (27) celebrates with left fielder Yordan Alvarez after hitting a home run. | IMAGN IMAGES via Reuters Connect1. SS Jeremy Peña2. DH Yordan Alvarez (L)3. 3B Isaac Paredes 4. 2B Jose Altuve5. LF Lamonte Wade Jr. (L)6. 1B Christian Walker 7. RF Taylor Trammell8. CF Lucas Spence9. C Christian VasquezWalker is now back in the starting lineup for the Astros for the first time since Saturday after he suffered right hip tightness and appeared in pain after his first at-bat in that game. The star first baseman did appear as a pinch hitter on Monday against the Marlins and looked to be held out for cautionary purposes. That makes complete sense given the previous injuries to the team. Although Walker only has a .233 average, he has increased his power this season. The 35-year-old started the season out on fire, and even led the American League in RBI's at one point. He has since cooled down. However, this could be the opportunity for him to reset and get back to it. He's hit 20 home runs and has 58 RBI so far. The Astros have to keep up the scoring given how unpredictable the pitching staff has been, and Walker is a big part of that. Taylor Trammell gets back-to-back starts while rookie Lucas Spence has now been in the lineup for five straight days. Miami Marlins at Houston AstrosWhere: Daikin Park, HoustonTime: 7:10 p.m.TV: Astros- Space City Home Network; Marlins- Marlins.TVRadio: Astros- KBME 790 AM/94.5 FM HD-2, KLTN-TUDN 102.9 FM; Marlins- WQAM 104.3, WAQI 710Starting PitchersHouston Astros pitcher Tatsuya Imai (45) delivers a pitch against the Milwaukee Brewers during the first inning at Daikin Park. Mandatory Credit: Erik Williams-Imagn Images | IMAGN IMAGES via Reuters ConnectAstros: RHP Tatsuya Imai (5-4, 6.06 ERA) vs Marlins: RHP Tyler Phillips (2-4, 3.48 ERA)The Astros don't really have experience against Tyler Phillips, as Nick Allen is the only player who has faced him before. Allen is not in the starting lineup. Meanwhile, this will be the Marlins' first time facing Imai as well. Imai has struggled in his last two starts in July and has an opportunity here with extended rest to put together a key quality start for Houston.Add us as a preferred source on GoogleFollow