HOUSTON -- Dallas Keuchel can afford to be flippant about his unusual success at home this season, especially considering that his extraordinary pitching doesn't appear set to wane.

The Astros ace left-hander treated his first career postseason home start as he did others throughout the regular season, throwing seven strong innings in Houston's 4-2 win over the Kansas City Royals on Sunday at Minute Maid Park in Game 3 of this American League Division Series.

The Astros took a 2-1 lead in the best-of-five series, and they could clinch a spot in the AL Division Series with a home win Monday.

Keuchel (2-0) tossed a season-high 124 pitches and dug deep into his reservoir to strand runners at third base in each of his final two frames.

The close of the seventh was particularly dramatic, with Keuchel staying in to face Royals center fielder Lorenzo Cain, who homered leading off the fourth inning. With Cain representing the tying run, Keuchel struck him out to cap his outing and preserve his lead.

"I figured he was going to let me pitch to their best hitter," Keuchel said of Astros manager A.J. Hinch, who paid a mound visit prior to the decisive at-bat. "And I thought I deserved it. Made a mistake pitch early in the game, but I felt like I really still had the energy and the pitch quality to get another out."

Keuchel improved to 16-0 at home with a 1.45 ERA by allowing one run on five hits and three walks with seven strikeouts.

Houston first baseman Chris Carter played some wobbly early defense but offset that by going 3-for-3. Carter finished a triple shy of the cycle, smacking a one-out double in the fifth inning and subsequently scoring the go-ahead run, then hitting a first-pitch leadoff homer in the seventh off lefty Danny Duffy.

Royals right-hander Edinson Volquez (0-1) was electric through four innings, relying on a fastball/breaking-ball mix that befuddled the Astros. However, he carried a tenuous 1-0 lead into the fifth and surprisingly started to unravel against the bottom of the Houston order.

Carter doubled after third baseman Luis Valbuena worked a walk, setting the table for catcher Jason Castro, who was hitless in nine postseason at-bats. Castro delivered a seeing-eye single to center field, scoring both Valbuena and Carter and delivering Houston a 2-1 lead.

"Good time to get my first hit in the postseason, that's for sure," Castro said.

The Astros tacked on insurance runs in the sixth and seventh. Right fielder George Springer doubled and scored off Volquez in the sixth, coming home when center fielder Carlos Gomez laced a first-pitch single to center with two outs. Carter added his first career postseason home run an inning later, a 393-foot blast to left field.

"He's hung in all year," Hinch said of Carter, who lost his starting job when his batting average dipped to .181 on Sept. 7. "It hasn't been an easy year for him. It's still been a relatively productive year for him. This guy's continued to hit homers and maintained his composure."

Volquez allowed three runs on five hits and four walks with eight strikeouts, departing with two outs in the sixth inning.

Royals left fielder Alex Gordon smacked a leadoff homer to left in the ninth off Luke Gregerson. The Astros closer rallied to strike out Cain with Ben Zobrist on first best to end the game and record his second save of the series.

"It's tough. It's a tough loss for the team," Volquez said. "We still have confidence that we can come back tomorrow and win the game.

"I thought I pitched pretty good tonight. I was pitching against Keuchel, who is a bulldog. He is a competitor. He can compete against anybody."

In Game 4 at Minute Maid Park, the Astros will send rookie right-hander Lance McCullers to the mound against Royals right-hander Yordano Ventura, who took the loss in the series opener.

"You got to go out and win," Royals manager Ned Yost said. "We know that. I don't think our mindset would have changed any if we won today. You got to go out and win tomorrow, so you just don't have much leeway now, but our guys I think are up to the task, and tomorrow will be an exciting day."

NOTES: Astros CF Carlos Gomez was in the starting lineup for the first time this series, batting sixth, and he hit an RBI single. Gomez homered in the American League wild-card win over the Yankees but aggravated the left intercostal strain that first sidelined him in mid-September. He appeared as a pinch runner in Games 1 and 2 of the AL Division Series. ... Royals manager Ned Yost was leaning toward starting RHP Yordano Ventura in Game 4 of the ALDS even before Ventura pitched a rain-shortened two innings in Game 1 on Thursday. Ventura threw just 42 pitches before being lifted following a 49-minute rain delay. ... Astros manager A.J. Hinch declined to name a starter should the series extend to five games. RHP Collin McHugh would seem to be the logical choice after winning the opener on Oct. 8, allowing two runs on four hits and two walks with one strikeout over six innings in a 5-2 victory.