Cubs expected to call up No. 4 prospect Ballesteros, place Happ on IL (source)

This browser does not support the video element.

CHICAGO -- The Cubs came into this season believing they had the depth -- both in the Major Leagues and among their upper-level prospects -- to withstand unexpected setbacks and still remain firmly in a postseason chase. That continues to be tested for the National League Central leaders.

After Monday’s 5-2 win over the Marlins, a source told MLB.com that left fielder Ian Happ was expected to be placed on the 10-day injured list prior to Tuesday’s game due to an oblique injury. Catching prospect Moisés Ballesteros (Pipeline’s No. 4 Cubs prospect and No. 61 on the Top 100) is in the plans to join the Cubs from Triple-A Iowa.

The Cubs have not confirmed the move, which comes shortly after the ballclub promoted its top pitching prospect, Cade Horton (No. 2/No. 35), from Iowa to help the pitching staff after lefty Shota Imanaga landed on the 15-day IL. A subsequent move will also be required to add Ballesteros to the 40-man roster.

Prior to Monday’s game, Cubs manager Craig Counsell indicated that Happ -- a three-time Gold Glove winner in left field -- was planning on “ramping up” his pregame work to test his side, which he initially injured on a swing in his first at-bat on Friday against the Mets. The manager noted that Happ did not do much activity on Sunday.

“We’re going to be cautious of this, obviously,” Counsell said prior to Monday’s game. “And I think he’s just trying to figure out, what is it? Is it nothing? Is it something? So, we gave him two days of very little activity and we’ll see what he feels like.”

The 30-year-old Happ has spent this season as the Cubs’ starter in left field and regular leadoff hitter, slashing .269/.364/.381 in 39 games. The switch-hitter has three home runs, nine doubles, 19 RBIs, 24 walks and 29 runs scored on the season.

With Happ out of the lineup for the last three games, Counsell has leaned on center fielder Pete Crow-Armstrong as the leadoff man. Seiya Suzuki, in turn, has moved back to the outfield after spending the majority of his time as Chicago’s designated hitter. Counsell can better rotate players through the DH slot now with Ballesteros joining the fold.

The Cubs’ catching tandem consists of Carson Kelly and Miguel Amaya, who are both enjoying strong starts to this season for the North Siders. On Monday, both catchers were in the lineup (Amaya behind the dish and Kelly at DH), while Happ remained sidelined.

Through 34 games with Triple-A Iowa this season, Ballesteros has slashed .368/.420/.522 with four home runs, seven doubles, one triple, 18 RBIs and 19 runs scored. He had drawn 12 walks, compared to 16 strikeouts, while spending the bulk of his time between catching and DH, plus one game logged at first base.

“He’s an enjoyable hitter to watch,” Cubs director of player development Jason Kanzler said earlier this season. “As much as we don’t know how to define the phrase ‘hitter-ish,’ he very much has the hitter-ish trait. It’s fun to watch a guy like that.”

Kanzler was quick to note that Ballesteros is still only 21 years old.

“What’s impressed me the most,” Kanzler said, “is remembering his age, and that he’s doing this as young as he is. He vaulted himself through the Minor Leagues using his bat. And what I don’t want anyone to forget is he’s making substantial progress catching.”

More from MLB.com