The former Notts County striker has returned to England to finalise paperwork.
"That's a problem to say a time frame with him,'' Backe told the New York Post. "His knee is fine, but there are some bones under his toe that is giving him problems and pain. Hopefully at the end of this camp in Arizona. He's been away for almost two months. He did some training until mid-January.
"He's not a heavy guy: He's a short, pacey guy and they are always coming back earlier. He trained up to mid-January and so we're talking about six weeks he's behind. If he's just fit, we can use him pretty quick.''