Hart suffered a concussion following a line drive to the face in a game against New Orleans on June 18 and was placed on the disabled list two days later.
Wells, meanwhile, may pitch Monday. He was listed as suffering a bone bruise in his calf stemming from a start last week.
"[Wells] had kind of a sore muscle in his elbow," Mason said. "He's over it. He's been off the medicine for the last few days, and he's ready to go probably about the 30th."
In a start against Albuquerque last Saturday, Wells lasted just two innings, giving up 10 runs on nine hits – three of which were home runs.
For his part, Hill was placed on the disabled list earlier in the week with what the Cubs termed a strained left hamstring and was sent to work with trainers in Mesa.
"He actually did it when he was out running," Mason said of Hill.
Samardzija Doesn't Miss Football
Despite signing a five-year, $10 million major league contract nearly 18 months ago, Jeff Samardzija is still quizzed from time to time by some members of the media about the sport he chose to give up in order to start his pro baseball career.
"No, not at all," Samardzija said Thursday when asked if he missed playing football.
Samardzija told Randy Peterson of the Des Moines Register that he was not sure if his contract with the Cubs stated that he cannot play football at a later date.
To Samardzija, it's a moot point.
"I'm not going to play football, so I don't really even know if there is a clause in there or not," the Cubs' pitching prospect said. "It's really irrelevant to me. I'm just here to play baseball, and do it for a long time."