Barnsley defender Bobby Hassell faces another month on the sidelines after having surgery on a troublesome left knee.
The 27-year-old full-back has not started a game for the Tykes this season and was complaining of pain in his knee.
The club's head physio Richard Kay confirmed the player's lay-off on Barnsley's official website.
He said: "Bobby has an appointment with the specialist again on Wednesday and hopefully he will be given permission to step us his rehab work and do some running.
"He will then have to go through a pre-season programme and get a good level of fitness. We will look to condense six weeks of fitness work into a month."
Butterfield signs on
Meanwhile, youngster Jacob Butterfield has signed his first professional contract with the club.
The 17-year-old defender is a product of the Barnsley youth academy and has signed a three-year deal at Oakwell.
Butterfield made his professional debut this season during Barnsley's Carling Cup tie against Newcastle, and academy manager Ronnie Branson revealed the teenager's progress has given all the youth players a lift.
"All our youngsters have been given a boost simply by seeing Jacob make that step up. He is one of them and he has proved there is a path to first team football through the academy."