Earing was one of the Saddlers’ standout performers last season but has not featured in any of the summer friendlies.
Asked when the 23-year-old could return to action, boss Michael Flynn said: “I’m not sure. With Jack, he’s missed all of pre-season.
“He had a reaction after running last Saturday. It’s one I just can’t put my finger on.
“It’s basically inflammation of the Achilles, which is making his calf tighter when he’s running.
“He’s going to have to be right as it’s a dangerous area to be messing with.
"If you go and your Achilles ain’t right, and it snaps, you’re in big trouble.”
Flynn added: “He’s playing catch up. He’s a naturally fit lad, but he’s playing catch up.
"He’s going to need three to four weeks, easy.
"He’s got to play games and get minutes, so watch this space.”