After the San Diego Padres lost three straight games to the Colorado Rockies last week to slip to 5-13 over the last 18 games, Padres manager Bob Melvin looked ahead.

“It would be great to go into the All-Star break on a winning run,” he said. “This is an important series.”

That series is the Padres-Diamondbacks set underway in San Diego. And through the first two of three games, Melvin has gotten exactly what he wanted — back-to-back wins.

On Sunday, the Padres will seek to end the first half of the season with a sweep of a team they have beaten nine times in their first 11 meetings.

But the Diamondbacks might have a force going Sunday in right-hander Merrill Kelly (8-5, 3.36 ERA).

“Kelly gives one strong effort after another,” Diamondbacks manager Torey Lovullo said after Kelly’s most recent quality start. “I can’t say enough about Merrill Kelly. He knows how to pitch, and he uses everything he has.”

In his first three starts this month, Kelly has given up five runs on 12 hits and six walks with 13 strikeouts in 20 1/3 innings. That’s a 2.21 ERA and a 0.885 WHIP. Half of Kelly’s starts this season fall into the quality category.

Kelly will make only his second start against the Padres this season. On April 8, he shut them out on four hits and two walks with seven strikeouts over four scoreless innings in a game the Diamondbacks lost 3-0.

It’s been that way all season.

The Diamondbacks are only 9-9 in Kelly’s starts, although the pitcher has yielded one or fewer earned runs in eight of his 18 outings.

Kelly is 7-2 lifetime against the Padres with a 2.43 ERA, a 1.197 WHIP and a .232 opponents’ batting average in 11 career starts. He is 4-2 with a 3.23 ERA in six starts in San Diego.

Opposing Kelly on Sunday with be Padres right-hander Mike Clevinger (2-2, 3.79), who will make his ninth start of the season. Clevinger has been the losing pitcher in each of his last two starts — giving up eight runs on 11 hits and three walks in 11 1/3 innings.

Before that, Clevinger made consecutive starts against Arizona on June 22 and 29. The Padres won both games as Clevinger gave up one run on six hits and three walks over 10 innings. Those are Clevinger’s only two appearances against the Diamondbacks in his career.

One of the issues with a Clevinger start this season is the fact that he’s completed six innings only twice in his return from a second round of Tommy John surgery.

Sunday’s start could see MacKenzie Gore or Nick Martinez piggybacking with Clevinger. The Padres are 6-2 this season when Clevinger starts.

“There are no more restrictions on Clev,” Melvin said recently. “But it’s worked out well when Martinez has piggybacked with him. It’s been like having two starters in the same game.”

But Martinez pitched during the first game of the Diamondbacks’ series while Gore had his last scheduled start before the All-Star break skipped to control his workload.

Skipping Gore’s last start means Clevinger will work on four days’ rest Sunday for the first time this season.

–Field Level Media