Collingwood utility Ben Johnson has become the second Magpies veteran in four days to have their AFL pre-season interrupted by injury.

Johnson strained a hamstring at training on Wednesday and, after having scans, is expected to be sidelined for three or four weeks, the Magpies said on Thursday.

Collingwood’s latest injury blow came after star forward-midfielder Alan Didak tore an adductor muscle on Monday, which the club predicted would keep him out of action for four weeks.

Johnson, 30 years old and a 224-gamer, is the second oldest player on Collingwood’s list, after 31-year-old Chris Tarrant.

He played 16 matches last year, including all three of the Magpies’ finals, but missed a large patch of games mid-season with a back injury.