Jake Arrieta's breakout first half is about to turn into a chance for a breakout season, but the Cubs are going to be careful with him anyway.
The right-hander will make his first start following the break on Sunday against righty Josh Collmenter and the D-backs as the clubs wrap up the three-game weekend set. Arizona will be looking to complete the sweep over cellar-dwelling Chicago.
Arrieta will be pitching on nine days rest for the second time this season. He could have gone earlier in the weekend, but the team is opting to tread carefully with the 28-year-old enjoying his best Major League season since debuting in 2010.
"In talking to [pitching coach Chris Bosio], he thought it was good to set Jake back a little bit," Cubs manager Rick Renteria said. "We know he's come off the injury early in the season. He's been throwing very, very well. He said, 'You know, let's push him back and give him a little rest.' I thought it was a good idea."
On the season, Arrieta owns a 1.95 ERA and 1.01 WHIP, numbers that would rank in the top-10 in baseball if he had enough innings to qualify. He didn't pitch until May 3 due to tightness in his shoulder during the spring. Other career bests for Arrieta include his strikeout rate (9.8) and strikeouts-per-walk (3.86).
In two starts since the Chicago-Oakland blockbuster made Arrieta the team's best remaining starting pitcher, he has allowed four runs in 13 2/3 frames (2.63 ERA) while limiting opponents to a .170 average.
Collmenter has enjoyed similar success of late, holding opposing teams to one or fewer runs in four of his last five games. That includes seven innings of one-run ball against Miami on July 9.
In those last five games (four starts), a stretch that started a month ago, Collmenter has a 2.96 ERA and 1.48 WHIP, with an ugly outing against the Braves -- five runs on 11 hits in six innings -- serving as the outlier.
Collmenter has dominated the Cubs, as he has limited Chicago to two runs in 14 1/3 innings in five games (two starts), including three scoreless innings of relief in 2013. No Cub, however, has seen him more than eight times.
The only Arizona batter with any considerable history against Arrieta is his old American League East foe, Aaron Hill. Hill is 4-for-11 (.364) with a homer and double off him.
Cubs: Club yet to name fifth starter
The trade of Jeff Samardzija and Jason Hammel to the A's left huge holes in the Cubs' rotation. Kyle Hendricks will get the first shot at filling one of the spots, but Cubs manager Rick Renteria isn't ready to name a fifth starter.
Tsuyoshi Wada, a 33-year-old lefty with a 2.77 ERA and 1.16 WHIP in Triple-A, and Dan Straily, who was part of the return from Oakland earlier this month, are two candidates. Straily has yielded four earned runs in nine innings in two outings for Triple-A Iowa after posting a 4.93 EA and 1.25 WHIP in seven Major League starts for the A's this season.
The Cubs first need a fifth starter on Wednesday against San Diego.
D-backs: Perez especially strong of late
Oliver Perez hasn't allowed a run in his last 8 1/3 innings spanning nine appearances dating back to June 20, striking out 15 in that span.
"He kind of wants the ball every day," D-backs manager Kirk Gibson said. "He runs every day. He long tosses every day. He has an extremely resilient arm. He knows how to pitch. He can get lefties out; he can get righties out.
"He gets ready in one hitter. You could almost call down there in the middle of an at-bat, tell him to get ready, stall and he'd be ready to go the next hitter. He's very polished. He's a great veteran to have on our team."
On the season, Perez owns a 2.00 ERA, 1.14 WHIP and 10 strikeouts per nine innings.
• Arizona shut down shortstop Chris Owings, who is working his way back from a strained left shoulder, through at least the weekend. He is eligible to return from the disabled list, but a visit to the doctor Friday indicated he isn't all that close to returning.
• The Cubs, 5-10 in July following a fourth straight loss on Saturday, are on pace for their worst month of the season record-wise.
• Sunday will be the Cubs' last game before beginning a stretch in which they will play 23 of 33 games at Wrigley Field.
Tim Healey is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.