John Rudge told the official web-site: "It's bad news for us and more bad luck," said Stoke's Director of Football, John Rudge.
"We were delighted to get Mark on loan because he brought in experience and competition and allowed us to give Neil Cutler a break.
"Mark did well for us at Gillingham. Now we are back to square one.
"It's just our bad fortune that a possible injury has cropped up so quickly.
Tony Pulis said: "I can't believe it,"
"Schwarzer has been for an x-ray and apparently nothing is broken, but clearly Boro can't take the risk and I can understand them wanting Mark back.
"But it is a real kick in the teeth for us, and now we must decide on our next move."