PHOENIX -- Following a weekend of excitement against the Mets, the Pirates came up short Monday in their 4-2, series-opening loss to the D-backs at Chase Field.

And for Chase De Jong, the struggles are beginning to add up in recent weeks.

De Jong allowed four runs on three homers, which were among the six extra-base hits he afforded the D-backs. A patient Arizona offense was able to sit on De Jong’s curveball that he tunnels off his four-seamer, and in the process, they got a few pitches down the middle, including on the back-to-back home runs from Pavin Smith and Josh VanMeter in the second inning.

So why didn’t the two pitches play like they did earlier in the season, when De Jong had a 4.26 ERA in his first four starts, only marred by one five-run outing? It comes down the four-seamer, he said.

Both the home run balls to Smith and VanMeter were called by catcher Jacob Stallings to be four-seamers up in the zone -- a pitch and location that De Jong calls his “bread and butter.” Instead, they were yanked down into the heart of the plate, and they were cranked. And De Jong feels something is off with the way he is landing on his left foot, in terms of timing and syncing up with his upper body, that’s amplifying the mistakes.

“We can go back and look at video to confirm and obviously have Oscar’s eyes on me when I throw my ‘pen, but I think that’s the thing,” De Jong said. “I’m just not getting my foot down on time to allow myself to let it go at the top.”

De Jong sees that as a connecting thread between a recent stretch of tough outings. The 27-year-old has allowed four runs or more in five of his nine starts this season, and four of those outings have come over his past five starts. Things are not trending in the right direction.

The right-hander had to work overtime to get through five innings, tossing a season-high 97 pitches. That’s also been a theme for De Jong in this recent go, as he’s needed 92 or more pitches to get through each of those four rough outings in the past five.

De Jong also had to grind through pain to complete his five innings on Monday. David Peralta ripped a 89.5 mph liner that deflected off the inside of the Pirates’ starter’s left knee. He used his adrenaline rush to dive and make a throw to first baseman John Nogowski for the out, but he was down writhing on the field for a few seconds.

After walking it off, De Jong stayed in and went five innings.

“Once I recognized where I got hit and that I could still bend my knee, I needed to try to get through that and give those boys [in the bullpen] innings,” said De Jong, recognizing the ‘pen was short one player after Kyle Crick was designated for assignment today without a corresponding active roster move.

“He’s got a significant bruise on the inside of his knee,” manager Derek Shelton said. “We came in after that inning, and it was already bruised and swollen. I give him credit for grinding through it.”

To get to the point De Jong has with the Pirates, though, he’s had to grind. He went from the Majors to independent ball and found a rotation slot with the Pirates. If there’s anyone who knows how to push through adversity, it’s De Jong.

The Pirates will have starting pitching decisions in the coming month. Steven Brault is on rehab assignment at Triple-A en route to Pittsburgh after he missed all of the first half with a lat strain. Mitch Keller, who was optioned after struggling in the first three months of the season, will get another shot with the big league club again sooner or later.

To make a strong case for his spot, De Jong knows what he needs to do to give himself the best chance.

“The three homers and the loss stink, but I’m able to navigate through that and I’m able to see that we did a lot of things well,” De Jong said. “We’re going to move on from this and figure this out.”