McCombe has not played since fracturing his cheekbone against Derby County in August.
He will feature in a behind-closed-doors friendly against Swindon Town on Wednesday, with the Robins boss Gary Johnson saying he just needs to build up his fitness.
"Jamie's cheek is fine and he's ready to play. Now we just need to get the rest of him fit. He was back training as normal last week and joining in with the other lads and he's working very hard to get back," he said.
"Our medical people say he's made a full recovery and he's been heading balls in training and doing full contact work. He has to get match-fit though. He needs games because playing is the only way to get match sharp."