Manager Gary Waddock told the club's official website: "The doctors say it may take six weeks, but Johnno's a good healer so we're hoping it will be four.
"He's doing rehab already, but we won't rush him back because you run the risk of making the problem worse."
Meanwhile, Chairboys midfielder Matt Bloomfield has returned to full training after treatment on a knee injury.
Source: BBC Sport
Source: BBC Sport