The Barons had a franchise-record 22 shots in the third period Sunday but couldn't get one past goaltender Tom McCollum as the Griffins took the lead early in the period and then extended it.
Just four minutes in, Chris Minard took a pass at the point and beat Barons goaltender David LeNeveu on his glove side to put the Griffins in front.
Just more than four minutes later, Francis Pare took a cross-ice pass from Joakim Anderson near the blue line. LeNeveu got a piece of the shot, but it trickled over the line to put Grand Rapids up by two.
“I thought we kind of got away from things that we've been doing well before,” Nelson said. “Sometimes that creeps in with three games in three nights. “It was one of the things we tried to guard against.
“The third just didn't go our way. Grand Rapids looked like they had more jump than we did, but they should've.”
The Barons (41-18-9) lost defenseman Taylor Chorney to injury in the first period. It is not known how long Chorney will be out. But Oklahoma City is expected to have defenseman Alex Plante in the lineup during next weekend's road trip. He has been out with a concussion.