HOUSTON -- A day after starting and hitting his first Major League home run, third baseman Ryan Wheeler was again in the lineup on Sunday. He hadn't started back-to-back games since joining the club on July 20.

Manager Kirk Gibson said Wheeler earned some starts with good at-bats as a pinch-hitter.

"[Pinch-hitting] really makes you get with it," Gibson said. "It's not like you're getting a consistent three or four at-bats a game. We saw some improvement there."

Gibson also felt Wheeler put in the work in the batting cage and in the infield before games.

With Wheeler starting, Chris Johnson was relegated to pinch-hitting duty for the second straight day. Johnson is hitless in his last 16 at-bats. He started two of the D-backs' past five games after starting in his first 13 as a D-back.

Gibson said before Saturday's game that he was trying to keep players fresh as they started a stretch of five games in four days. Justin Upton also had the day off on Sunday.

Gibson: Time to make move is now

HOUSTON -- The D-backs concluded a stretch of 16 road contests in their past 19 games on Sunday. Regardless of Sunday's outcome, the D-backs will finish with a winning record on the road over that span, taking nine of the first 15 road contests.

They swept the Dodgers, lost two of three to the Phillies, split four with the Pirates, won one of three against the Cardinals and looked to sweep the Astros on Sunday.

"We started out very slow in St. Louis, but so far we've salvaged," Gibson said. "Getting the last game [in St. Louis] was big and the way we did it was even better. We've got a tough stretch coming up here. We can't let our guard down."

With ground to make up in the National League West -- the D-backs woke up on Sunday five games back of the Giants and 4 1/2 games back of the Dodgers -- Gibson knows the time to make a move is now.

"Time is of the essence," Gibson said. "We need to certainly win all of our series or average out that way."

After Saturday's game, Gibson thought back to his experience with the 1987 Detroit Tigers, who were 3 1/2 games behind the Blue Jays with eight games remaining. The Tigers surged back to make the postseason.

"You have to have conviction that anything's possible," Gibson said. "We know we've made it hard. Today's the next day. We have to go out and play a good game and beat those guys. Every day after that is just more critical."

The D-backs understand what they need to do to make the postseason: play their best baseball of the season.

"The pressures change everything." Gibson said. "That's the fun part."

Worth noting

• Left fielder Jason Kubel batted third in Sunday's lineup after missing the first two games of the series with a stiff neck.

• Right-hander Josh Collmenter, on the disabled list with ulcers since Aug. 10, came through a bullpen session on Saturday well. Gibson said Collmenter will run through baseball activities on Monday at Chase Field, followed by a simulated game at Salt River, the D-backs' Spring Training facility, later in the week.

Collmenter is eligible to come off the disabled list next Saturday.

• On Sunday night, Gibson and general manager Kevin Towers will discuss their pitching options for Wednesday's home doubleheader against the Marlins. Wade Miley would be on regular rest, as would prospect Trevor Bauer, who threw on Friday at Triple-A Reno. The D-backs can add a 26th player for Wednesday's games.

Bauer has made four starts for the D-backs, posting a 6.06 ERA. In four starts since being demoted to Reno, Bauer has a 2.96 ERA. On Friday, he tossed a complete game with 12 strikeouts against Round Rock.