The Greyhounds are still in eighth place in the OHL's Western Conference but they blew a chance to move into sole possession of seventh in front of more than 3,400 fans at the Gardens on Friday night.
Outshooting the Hounds 51-26, the visiting Guelph Storm outscored the Soo 6-1 as defenceman Niko Tuomi returned home to haunt his old team.
The 19-year old Tuomi, who was traded by the Hounds to Guelph earlier this season for fellow blueliner Corey Leclair, had a goal and two assists for the Storm, which moved two points up on the Soo into sole possession of seventh place.
Guelph has a game in hand on the Hounds, who have four to play, including one at home on Sunday to the sizzling Windsor Spitfires.
Sean Stefanski had the only goal for the Soo in the loss to Guelph. Despite the Hounds' fourth setback in their last six games -- they've given up 26 goals in those losses -- the Soo still holds a six-point lead on the Erie Otters for the eighth-and-final playoff spot in the Western Conference.
Erie, which has a game in hand on the Soo, lost 3-2 to the London Knights on Friday.