Arenado completed a five-game suspension on Wednesday, when the Rockies lost 10-2 at Pittsburgh to end a 5-2 road trip that began in Washington. The Rockies were off Thursday after playing 17 consecutive days.
Arenado was suspended for charging the mound on April 11 when San Diego's Luis Perdomo threw a 96 mph fastball behind him. Outfielder Gerardo Parra's actions in the ensuing brawl resulted in a four-game suspension, which Parra is expected to begin serving Friday with the return of Arenado.
The status of right fielder Carlos Gonzalez could complicate matters. He made a sprawling catch in right center of Starling Marte's liner to open the fourth inning on Wednesday, and for precautinary reasons was lifted for a pinch hitter in the fifth with a slight strain of his lower right hamstring.
"We'll see how it sets up here over the next couple of days," Rockies manager Bud Black told reporters Wednesday. "We are hoping it resolves itself quickly, but we're not quite sure where this is headed.
"He's sore. It doesn't look to be a significant hamstring strain at this point, but it's still concerning. We'll see how he is in a couple of days."
An iffy weather forecast on Friday and Saturday could buy time for Colorado (11-9). However, the Cubs (8-8) will be eager to play, having already endured five postponements in three weeks this season.
Parra's suspension will reduce to the active roster to 24 players, and Gonzalez could make it 23 with three outfielders -- Ian Desmond, who has made 11 of his 18 starts at first base, Charlie Blackmon and reserve Michael Tauchman, who has made four starts and is 1-for-20 with one walk and nine strikeouts.
Depending on Gonzalez's status, the Rockies could opt to bring an outfielder from Triple-A Albuquerque to Denver in case they decide they can't be short another outfielder in addition to Parra.
Candidates for a promotion would be Noel Cuevas, a right-handed hitter, and Raimel Tapia, David Dahl and Jordan Patterson, all of whom bat left-handed.
Jon Gray (1-3, 6.23 ERA) has made 62 starts in the majors but will make his first career start against the Cubs. He's 0-2 with a 10.13 ERA in his past two starts against San Diego and at Washington, giving him consecutive losses for the first time since Sept. 23-29, 2016.
Cubs starter Kyle Hendricks (0-1, 3.71) has allowed two homers in each of his past two starts, including his most recent outing Friday against Pittsburgh when he gave up two runs in six innings in a 6-1 loss.
Hendricks is 1-2 with a 4.04 ERA in six starts against the Rockies and 1-1 with a 3.28 ERA in four starts at Coors Field, allowing two or fewer earned runs in three of those games.
Colorado is last in the National League in both batting average (.214) and on-base percentage (.285) and 12th in OPS (.666). But more homers (27) than doubles (25) and strong outings by their starters until Wednesday have helped the Rockies win six of their past eight games.
While the Rockies will be looking to get their stagnant offense going, Chicago will be trying to find some flow in a season that to date has been badly disjointed.
The Cubs had three games postponed at Wrigley Field this week. They made up a game with the St. Louis Cardinals on a scheduled off day Thursday, winning 8-5 to match their season-high two-game winning streak for the second time.
"It has been a little bit of a choppy schedule," Chicago general manager Jed Hoyer told reporters this week. "I think that's made it hard to get in much of a rhythm. But I think that we had some games early (where) we let it get away a little bit."
Drawing on a golf reference, Cubs manager Joe Maddon put it another way and said: "You just play through the bad lie. That's all there is to it. There's nothing you can do about it."