Man Utd boss Ferguson includes Buttner in his 'ones to watch' list
Ferguson expects the Dutch fullback to be pushing for a regular start next season.
He said: "I would expect us to have a real good challenge next year.
"Rafael has proved how much he has developed this season, while David De Gea's progress in goal has been superb.
"We've got to deal with one or two players getting older - but we're not so bad in terms of protecting most positions."