One of my favorite TV series of all time is the Battlestar Galactica reboot on Sci-Fi channel, and one of the great episodes centered on the crew of the ship setting up a boxing ring, calling out a crew member, and you step in the ring and battle it out. The purpose being carrying on beefs between people fosters disharmony, so one way to bring back harmony within the crew is to get in the ring, duke it out, then bury the beef and exit the ring as friends again.
S6 Ep 15 was a good one overall for BlueBloods, but it started off with Garrett and Frank screaming at each other full throat. This wasn't the usual arguing and snark that they exhibit pretty much every episode -- this was something worse. Garrett was basically telling Frank to grow up and that the Mayor shouldn't have to come over and ask Frank to stay on, and Frank was acting a little pompous windbaggey by wanting the Mayor basically to come by and stroke his ego.
I've wondered why Garrett sticks around when he could probably call up an Ad Agency and make 5x what he's making, and the show had that exact issue in S5 when a buddy of Frank's came by to offer Garrett a job, and Garrett did not accept the job basically out of loyalty to Frank, but at some point, do you really want to have a screaming, unhealthy relationship with your boss?
I'd put my money on Garrett taking Frank in 3 rounds -- Garrett could be surprisingly nimble on his feet -- duck and weave, duck and weave-- and Frank might have a lot of power in his punches, but if Garrett has speedy feet, he might be hitting a lot of air.