McDonagh will miss Monday night's game against the New Jersey Devils because of the concussion, the team announced.
He was knocked to the ice bySimmonds' punch in the Rangers' 3-2 shootout victory. Simmonds was retaliating after McDonagh committed two penalties against him.
Simmonds received a five-minute match penalty and game misconduct for punching McDonagh. Upon the announcement of the penalty, Simmonds hurled his stick on the ice toward the officials before heading up the tunnel.
When talking with reporters Monday, Vigneault said he was surprised by the league's decision to not suspend Simmonds, who was in the lineup for the Flyers' 3-2 loss to the Washington Capitals on Sunday.
"What I didn't expect was the reaction from the league," Vigneault said. "An All-Star player gets sucker-punched, goes down. I wonder if that's [Sidney] Crosby, what happens? What are the consequences?
"And on top of that, a player breaks his stick, throws it at the referee. In the rulebook, that's automatic. It's three games. And nothing happens. It's not even on the sheet after the game."
McDonagh crumpled to the ice with 9:24 left in the first period after Simmonds threw a left cross to McDonagh's jaw during Saturday's game.
McDonagh received two penalties, one for slashing Simmonds and one for cross-checking him before Simmonds retaliated with the punch.
"I was just happy that [Simmonds] was still standing after the cross-check he took to the side of the head,'' Flyers coach Dave Hakstol said after Saturday's game.
Simmonds turned down reporters' requests for comment Saturday.
ESPN's Joe McDonald and The Associated Press contributed to this report.
Stepan nets shootout winner for Rangers
Defenseman Keith Yandle scores in the final moments of regulation and Derek Stepan scores the winner in the shootout to give the Rangers a 3-2 victory over the Flyers.