Leitch-Smith, 19, is back at Gresty Road, along with fellow youngster Chris Clements, after scans revealed Donaldson suffered a fractured fibia in the league defeat at Bournemouth at the weekend.
On Donaldson's injury, a club spokesman said: "Clayton has fractured the fibula in his lower leg. A rehabilitation period of six weeks is the best outlook but it may well be November before we see him again."
Meanwhile, Alex face an anxious wait to discover the extent of the back injury that forced Mat Mitchel-King off in the Johnstone's Paint Trophy defeat to Stockport on Tuesday night.
The summer signing from Histon had to be replaced after half-an-hour and is set to undergo a scan.