The D-backs took 2 of 3 from the Cubs last week in Wrigley Field, sending the world champs on a mini-skid has jeopardized their standings atop the NL Central. Chicago (59-54) has gone 2-4 since the Diamondbacks left town, allowing the streaking St. Louis Cardinals to pull within one game of first place.
The Cubs will have to carry on for the short-term without their hottest hitter -- catcher Willson Contreras, who suffered a hamstring injury in Wednesday's loss at San Francisco. There has yet to be any official word on the seriousness of the injury -- but Contreras is rumored to be out for two to four weeks, with Alex Avila taking over behind the plate. Contreras has hit 10 home runs since the All-Star break -- second most in the majors -- and had hit five in six games prior to his injury.
The D-backs (64-50), meanwhile, have also lost 4 of 6 since last week's series at Wrigley -- including their last two against the Dodgers. They are still 5 ½ games clear in the battle for an NL wild-card berth, but they've fallen a game behind Colorado.
Walker wasn't involved in the decision in his most-recent start on Saturday against the Giants. He had a shutout through six innings but then gave up two doubles and a home run to the first three batters in the seventh, and the D-backs went on to lose 5-4 in10 innings.
He is 4-3 with a 3.11 ERA in 10 starts at Chase Field and has held the opposition to three earned runs or fewer in 12 of his last 13 starts.
"He's had a lot of really good games where he might not have had the greatest results, maybe made a mistake or two that led to him giving up a couple of extra scratch runs," Arizona manager Torey Lovullo said. "Every time he is out there, he has given you five-plus innings and you look up at the scoreboard and he's got close to 10 strikeouts. That is really nice to feel when you are the manager, knowing you are going to get that on a pretty consistent basis. We're not going to take that for granted. We know he is prepared for every start."
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Cubs starting pitcher John Lackey (9-9, 4.81 ERA)
Lackey struggled throughout the first half of the season but has come on strong lately, going 4-0 with a 3.00 ERA in four starts since the All-Star break. Manager Joe Maddon has managed his workload carefully -- limiting him to no more than six innings or 95 pitches in his last 10 starts.
The biggest problem for Lackey has been the long ball. He's surrendered 27 home runs -- sixth most in the majors -- and his rate of 2.03 per nine innings is second for all pitchers with 100 or more innings. But he's given up just three homers in his last five starts -- coinciding with his recent turnaround.
Lackey is 4-0 with a 2.76 ERA in five career starts against the Diamondbacks. He last faced them in June of 2016 and worked six shutout innings, giving up five hits and two walks while striking out nine.
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Manager Torey Lovullo has been impressed with the play of shortstop Ketel Marte, who has stretched his hitting streak to 10 games (14 for 34 with four doubles, two home runs and six RBI) even while dealing with the death of his mother in a car accident in the Dominican Republic.
Daniel Descalso has displaced Brandon Drury as the regular second baseman against right-handed pitching, and he's coming off a three-hit night against the Dodgers on Thursday. "He's a trusted player," Lovullo said, explaining how Descalso has earned his way into an increased role. "The heartbeat never changes. He executes when he's supposed to."
The D-backs are hoping to see center fielder A.J. Pollock heat up. He struck out three times on Thursday and is 4 for his last 25, dropping his average from .303 to .284.
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First baseman Anthony Rizzo had a big series against the D-backs at Wrigley, going 5 for 11 with three walks and two home runs. He leads the Cubs with 26 home runs and 71 RBI.
In addition to being without Contreras, shortstop Addison Russell is on the disabled list with a foot injury. Javier Baez has moved over from second base to shortstop, with Ben Zobrist and Ian Happ splitting time at second. Zobrist, who was a big part of the Cubs' success a year ago, is hitting just .225 with eight home runs. Happ is in a 6-for-36 skid over his last 13 games, with 15 strikeouts.