Celtics lock in on defense to hang on for ugly win over Pacers

BOSTON — The Celtics remain the best team in basketball with a 37-11 record following Tuesday night’s win over the Pacers. But as great as it’s been with the Celtics, it’s not always going to be pretty. That was the case Tuesday night, but Joe Mazzulla likes it that way. Yes, the Boston head coach likes when the going gets tough for his team. But he has a good point: There isn’t much to learn when a team wins in blowout fashion every night. Grinding out wins builds character, and sharpens a team’s mettle for when things really start to count in the playoffs. Monday night’s win over the Pelicans wasn’t pretty, as the C’s needed to overcome a 17-point…