PHOENIX — Arizona Diamondbacks pitcher Zac Gallen continued his impressive start to the season on Saturday, tossing six innings of one-run ball, but closer Mark Melancon struggled in a 4-2 loss to the Chicago Cubs at Chase Field in Phoenix.

Gallen came into the outing having the lowest ERA by a starting pitcher through his first five starts at 1.06, edging Randy Johnson’s 1.24 ERA to begin the 2000 season.

The 26-year-old righty allowed two hits while striking out nine and walking one on 96 pitches.

One of those knocks was Gallen’s only mistake of the game, a home run in the fourth inning off the bat of Yan Gomes.

“Zac I thought had a couple of really clean, good innings,” D-backs manager Torey Lovullo said after the game. “There were some batters that were a little bit stubborn which drove his pitch count up.”

“We were thinking about getting him through that seventh inning but at 96 pitches, it was time so we pulled the plug.”

Cubs pitcher Kyle Hendricks kept the D-backs’ bats just as silent, allowing five hits and one run in 5.2 innings while striking out two and walking two.

Arizona opened the scoring in the second inning, as Nick Ahmed drove home Ketel Marte with a single.

Each bullpen kept the opposing teams off the board through the latter half of the game.

Noe Ramirez and Joe Mantiply contributed two scoreless innings for the D-backs, while Scott Effross, Daniel Norris and Mychal Givens turned in 2.1 scoreless innings for the Cubs.

Melancon, after recording a save in a win against the Cubs the evening prior, struggled coming into a tie game in the ninth inning.

Melancon allowed the first three batters to reach, two walks and a single, before Gomes once again came through for the Windy City faithful with an RBI single to break the tie.

That would be it for Melancon as he got the hook for J.B. Wendelken, who allowed two of Melancon’s runs to score before stopping the bleeding.

“I wasn’t on the plate, they had good strike zone awareness,” Melancon said.

Lovullo blamed Melancon’s poor outing on the effectiveness of his cutter.

“He’s got to execute a little better with the command of his cutter and that’s what we’re going to talk to him about,” Lovullo said.

It marked the third time out of his last five outings that Melancon has allowed a run, each time coming into a tie game in the ninth inning.

Melancon was tagged for three runs in a loss to the Colorado Rockies on May 7, and four runs in a loss to the Miami Marlins four days later.

“This is unusual and not to go on any longer for sure. I can’t say the situation is a factor, it’s ironic,” Melancon said. “This is my job, in a tie situation … I need to take care of it.”

Lovullo was not ready to make a decision on the future of Melancon’s position as the team’s closer, who left the game with an 8.49 ERA and five losses on the season but having converted on seven of eight save opportunities.

“We’re mindful of everything that’s happening, we’re all having discussions about what’s going to put this team in the best position to win baseball games and those discussions will continue to be had over the course of the next couple of days,” Lovullo said, comparing the situation to Fernando Rodney in 2017 who went on to save 39 games and help the Diamondbacks to a National League Wild Card berth.

Melancon said his head is in a good spot and he’s going to stay positive.

“I have all the confidence in the world that I’m going to bounce back and this is going to be a great year,” Melancon said. “It’s just kind of crazy right now.”

The D-backs got one run back in the bottom of the 9th inning as Daulton Varsho drove home Alek Thomas with an RBI single, but Cubs reliever Rowan Wick struck out the next two batters to slam the door.

The D-backs look to win the series on Sunday as Humberto Castellanos takes the hill for Arizona against Justin Steele.

First pitch is 1:10 p.m. and all the action can be heard on 620 AM and 98.7 FM HD-2.