Top Cubs prospect Anthony Rizzo left Tuesday's game early with an apparent knee injury, but team president Theo Epstein said the first baseman wasn't seriously hurt.

Rizzo walked off the field in the sixth inning with a slight limp but under his own power after sliding into the fence in front of Triple-A Iowa's dugout while attempting to catch a foul ball hit by Omaha's Kurt Mertins. Epstein said Rizzo will be seen by an orthopedist, but that he checked out after seeing Iowa's training staff.

"He bumped his knee. .. he'll be OK," Iowa Cubs manager Dave Bialas told the Des Moines Register. "I can't tell you any more than he'll be OK."

Rizzo, in line for a promotion as he leads the Pacific Coast League with 22 home runs, has been particularly hot lately with consecutive two-homer, four-RBI games coming into Tuesday.

Bialas said he wasn't sure if Rizzo would play on Wednesday. MLB.com' No. 31 top prospect is hitting .367 with 22 home runs and 57 RBIs and leads the Minors with a .753 slugging percentage and 1.182 OPS.

Monday's multi-homer game was Rizzo's sixth such performance of the season. In his previous two contests, the 22-year-old first baseman was 6-for-9 with 19 total bases and eight RBIs.

Rizzo went 0-for-2 in the 9-4 loss while facing Omaha starter Jake Odorizzi, the Royals' No. 4 prospect, who allowed two runs on four hits over 5 1/3 innings to pick up his fourth Triple-A win. Odorizzi struck out seven to improve to 4-0 since his promotion from Double-A Northwest Arkansas, where he was 4-2 with a 3.32 ERA in seven starts.

Rehabbing Cubs catcher Geovany Soto went 1-for-4 with a double and a strikeout in his second Minor League game. Soto, 29, underwent arthroscopic surgery on his left knee on May 17 and has been on Chicago's 15-day disabled list since.

"It's just a matter of getting at-bats and getting my timing back," Soto told the newspaper. "Hopefully I'll get there soon."