Romero only left United last summer as he came off contract.
A source close to the goalkeeper has admitted that Romero 'would always come back' to Old Trafford if an opportunity presented itself, says the Manchester Evening News.
The 35-year-old failed to make a single appearance during his final campaign with the Red Devils, having fallen down the pecking order. But with Dean Henderson leaving for Nottingham Forest, an opening has emerged.
And Romero would be keen on returning as cover for David de Gea.