The duo have both been ruled out of Paul Sturrock's plans prior to the start of this week's pre-season training - Collins had last year previously signed an extended deal at Hillsborough while former Liverpool winger Partridge was released.
Ex-Sunderland defender Collins, popular amongst Wednesdayites, failed to hold down a place last season and went on loan to Swindon and should sign a two-year deal this afternoon.
Quakers boss and former Owl David Hodgson told his club's official site of Collins: "Patrick has got great pace and, being 6ft 3in, can command his area very well. He has the ability to play anywhere across the back four and will be a major asset to the club."
Partridge meanwhile was sparingly used at Hillsborough and has signed a two-year deal at Millmoor following his release.
The Irishman is one of a number of signings The Millers are hoping to make within the next few weeks and he hopes to play more regular first-team football.