Sheffield Uniteds plans for Saturdays South Yorkshire derby at Barnsley have been disrupted by news that Chris Armstrong has undergone surgery on his groin after losing Mason Plumlee Jersey his battle to go under the knife.Armstrong, who is adept at playing Josh Jackson Jersey both defensively and going forward, had initially hoped that his injury would not require surgery, but now manager Kevin Blackwell reckons Stretch will be out of contention for up to four Sviatoslav Mykhailiuk Jersey weeks after surgeons reattached part of Armstrongs groin to the bone.We are hoping weve caught it in time, Blackwell told the clubs official website. The tear is only slight and he might only be out for two to three weeks, four at the outside Reggie Jackson Jersey it depends on how Chris reacts to rehabilitation.Meanwhile, striker Luton Shelton has joined the United players jetting off after internation call-ups. Shelton, called up for Bruce Brown Jr. Jersey Jamaicas friendly with Trinidad and Tobago later on this month, joins Gary Naysmith, David Cotterill, Stephen Quinn and David Carney on the list of continental Blades representing their respective countries.