In slow-motion, it really appears that O'Connor used his foot in a kicking motion to influence the puck into the goal. The officials, however, did not think so and upheld their call as the Avs took a 1-0 lead in the first period. By no surprise, this call had Flyers fans on social media in an uproar.
Although the Flyers lost 7-4, a first period goal to take an early lead is a massive momentum shifter. If that goal was taken off, there is no telling where momentum could tilt.