Billy McKinney, the Cubs' third-ranked prospect, will miss the rest of the season after suffering a hairline fracture in his knee on Thursday.
"He won't play anymore this season," said Buddy Bailey, McKinney's manager at Double-A Tennessee. "He had a hairline fracture, it showed up on the X-rays the next day."
The 20-year-old outfielder fouled a pitch off his knee during a game against Chattanooga and was placed on the disabled list Saturday. Bailey said the 2013 first-round pick will fly to Chicago on Wednesday to be re-evaluated by doctors.
"He's gonna go to Chicago to see the orthopedic guys up there -- leave Wednesday and see them Thursday," Bailey said. "Obviously, from what they see and what information they have, then his diagnosis and how long he'll be out, whatever his process is to get healthy again, those guys will be knowing what they need to do Thursday."
McKinney tweeted on Tuesday that he hopes to return to the field as soon as possible.
"Thank you everybody for the kind words and support!" he wrote. "Means the world! Going to stay positive and come back ASAP."
McKinney was hitting .300 with seven homers, 64 RBIs and a .371 on-base percentage in 106 games this season between the Smokies and Class A Advanced Myrtle Beach. The lefty-hitting outfielder batted .340 wth the Pelicans before getting promoted on May 14.
McKinney hit .264 with 11 homers and 69 RBIs in 126 games last season across two levels as an MiLB.com Cubs Organization All-Star. He was acquired from the A's along with Addison Russell and Dan Straily last July 5 in the deal that sent pitchers Jason Hammel and Jeff Samardzija to Oakland.
Cubs' Edwards placed on DL
Carl Edwards Jr., the Cubs' top pitching prospect, also landed on the DL on Tuesday due to a callous on one of his fingers.
Cubs general manager Jed Hoyer said Edwards "had a callus on one of his release fingers," MLB.com's Carrie Muskat reported.
Edwards, a 23-year-old right-hander, is 5-3 with six saves, a 2.87 ERA and 73 strikeouts over 53 1/3 innings in 34 relief appearances this season for Tennessee and Triple-A Iowa. The 6-foot-3 righty last pitched on Monday, when he allowed a run without recording an out against Las Vegas.
Vogelbach close to returning
Bailey also gave an update on Cubs No. 13 prospect Dan Vogelbach, who's rehabbing in the Rookie-level Arizona League and has been sidelined since July 3. Bailey said the first baseman, who was slated to play in five rehab games, could return to Tennessee this weekend.
"If all goes well, he feels good, hopefully, he can get back east with us. Getting those [rehab] at-bats are going to help sharpen him up quicker, he's a very disciplined hitter," he said. "I expect him not to take very long to get back into the swing of things."
The 22-year-old -- Chicago's second-round pick in 2011 -- is hitting .295 with five homers and 34 RBIs in 64 games this season.