CHICAGO -- The next test has been lined up for Cubs closer Craig Kimbrel. And if everything goes according to plan, the right-hander could be back for the ninth inning by the time the Cardinals arrive at Wrigley Field later this week.

On Monday, Cubs manager Joe Maddon noted that Kimbrel will face hitters in a simulated setting prior to Tuesday's game against the Reds. Barring any setbacks, that would put the closer on target to come off the injured list by the weekend, following a bout with right elbow inflammation.

"It's possible," Maddon said before Monday's game. "He's been really trending in the right direction. So, if he comes out tomorrow and does that really well, we'll make our next plan. But, there's no reason to hold him back if he feels well."

Kimbrel has completed two bullpen sessions since landing on the IL earlier this month. The closer originally felt he would be ready to rejoin the bullpen by Thursday, but his recovery was more gradual than initially anticipated. Kimbrel's most recent mound workout consisted of 20 pitches on Sunday, and the results were encouraging, per pitching coach Tommy Hottovy.

Cubs president of baseball operations Theo Epstein agreed that the upcoming weekend series against St. Louis is a realistic target for Kimbrel's return.

"Yeah, that's why the Tuesday sim game is there," Epstein said. "Regardless of how well that goes, he'd probably need a day down after that. I'd say anything is possible after that."

Who leads off?

Anthony Rizzo was recently installed as the new leadoff man for the Cubs, who have used 11 players in that role this season. With the first baseman now potentially out for the rest of the regular season with a sprained right ankle, Maddon has to alter the top again.

"Stability is less important than production," Epstein said.

Maddon noted that he will lean on 38-year-old Ben Zobrist for that role, even if it means pulling the veteran after a few at-bats to keep him fresh. Zobrist, who recently missed four months while on the restricted list, also received some built-in days off (mostly against lefty pitchers). Maddon will need to find a solution for the No. 1 slot for those games.

"Someone Joe feels good about getting on base up there," Epstein said, "whether it's one of our best hitters who might traditionally hit in the middle of the lineup, and move him up there like we did with Anthony, or Zo or whomever. It's just, try to get someone who we have a good feeling about getting on base a couple of times."

Entering Monday, the Cubs ranked 30th in the Majors in average (.208) and on-base percentage (.289) out of the leadoff spot this season. Rizzo has a 1.028 OPS in his career as a No. 1 hitter -- the highest mark in MLB history among batters with at least 200 plate appearances -- and has hit .421 (8-for-19) in six games in that role this year.

Russell takes step forward

Prior to Monday's game, Cubs shortstop Addison Russell went through light bunting drills and hit off a tee during early batting practice at Wrigley Field. That marked Russell's first baseball activity since being hit in the head with a pitch one week ago.

Russell remains in MLB's concussion protocol and is not eligible to return from the concussion list until Thursday at the earliest. Until then, he will be required to keep passing check marks in MLB's protocol before ramping up baseball-related drills.