T.J. Oshie scored the lone goal in the shootout, Jaroslav Halak stopped all three Chicago shooters in the extra session and the St. Louis Blues defeated the Blackhawks 3-2 on Thursday night.
David Backes scored a power-play goal for St. Louis, while Alexander Steen was credited with an even-strength score in regulation in the Blues' first road game.
Chicago's Marian Hossa scored on a breakaway and set up Brandon Pirri's first NHL goal in regulation. All but one of the Blackhawks' (4-1-2) first seven games have been decided by one goal.
The Blues (5-1-0) started the season with five straight home games, and won the first four before losing 6-2 to San Jose on Tuesday.
Chicago's Corey Crawford made 26 saves and Halak had 27.
Both goalies made a handful of tough stops early before Pirri opened the scoring at 7:42 of the first.
After taking Hossa's perfect pass, Pirri sent a one-timer from the left circle that ticked off the post and into the upper left corner of the net.
Backes' power-play goal at 10:14 of the first tied it at 1. He was parked in front of Crawford and deflected in Jay Bouwmeester's wrist shot from the left point.
The Blues dominated early in the second period. Any momentum was broken when St. Louis' Barret Jackman hit Chicago star Patrick Kane hard from behind and was sent off for boarding at 7:18.
Hossa put Chicago ahead 2-1 with 2:38 left in the second on a breakaway. After the puck slipped past the Blues' defense, both Hossa and Patrick Sharp skated in alone, and Hossa fired a shot past Halak on the stick side.
Steen was credited with a goal 51 seconds later that was inadvertently knocked in by Chicago defenseman Duncan Keith and tied it at 2.
Steen was 30 feet out in the slot, and deflected Bouwmeester's shot from the point. The puck slid to the right side of the crease where Keith was trying to tie up Backes, but Keith swept the puck on goal and past Crawford.
The Blackhawks and Blues are expected to battle at the top of the Central Division, and the rivalry was reflected in increasingly physical, sometimes chippy play on Thursday. Chicago enforcer Brandon Bollig and St. Louis' Roman Polak fought midway through the third.
Crawford made a tough close-in save on Alex Pietrangelo with just over seven minutes left to keep it tied.
Halak made an alert save on Brandon Saad 33 seconds into overtime with Jonathan Toews closing in for a rebound. Jackman's shot hit the post 3:17 into the extra period.