Belichick showered Reed with praise as the Patriots prepare to face the Ravens in Sunday's AFC championship game.
"Can't say I've ever coached against anybody better than Ed Reed in the secondary," Belichick said.
The Patriots have played the Ravens six times during the regular season and once in the postseason. The only win the Ravens own against the Patriots came in 2010 in a 33-14 victory in the AFC wild-card round at Gillette Stadium.
Over the years, Belichick has become familiar with the play of Reed and Ray Lewis and the reputation of the Ravens' defense.
"They have some truly great players on the defensive side of the ball, future Hall of Famers, guys that are just really dominant at their position and have been for a number for years, or in Ray [Lewis] and Ed [Reed]'s case, about a decade," Belichick said.
He went on to add, "I don't know how much more savvy they could be. They're two of the greatest players to ever play the game, on the same team on the same defense for so many years.
"I don't know where to start. The play Ed Reed makes at the end of the game against Houston last week, I think that says it all, really. He's playing one side of the field trying to stay over the top of [Andre] Johnson, who they single up on the backside. I'm sure that they were looking for him.
"If he had single coverage, they'd want to throw it up to him, but Reed is over the top of him but they throw the Hail Mary to the other side and he comes all the way across the field and makes the play; really kind of a game-saving play. I'm not sure that if he hadn't made it, I don't know what would have happened there. Those are the kinds of plays he makes.
"He probably covers more field back there as a single safety than most teams can cover with two. He's got great instincts, he's a tremendous player. Ray Lewis, everything he brings to the game, his playmaking ability, his leadership, his experience, his ability to get people around him to play better both by his communication and anticipation and leadership and football savvy on the field. Those two guys, it would be really hard, I think, to put anybody even in their class, let alone above them. They're tremendous players with tremendous careers."