He probably was right — and this was in a game that saw Atlanta Hawks forward Paul Millsap go off for 45 points.

Smart scored 20 points, grabbed eight rebounds, handed out five assists and played great defense on Millsap, as the Celtics, down by 16 in the third quarter, evened the best-of-seven, Eastern Conference first-round playoff series at two games apiece with a 104-95 overtime win.

Millsap scored only two points over the final 5:33 of regulation and the entire overtime.

Smart, only the second player since 1992 to register at least 28/8/5 off the bench in an NBA playoff game, scored 11 consecutive points for the Celtics in the fourth quarter. He then opened the overtime with a pair of assists to Amir Johnson. Boston never trailed in the OT, during which Atlanta hit just one of its 11 shots.

Smart, fined $5,000 for flopping in Game 3, admitted he was a little surprised when coach Brad Stevens told him to try to stop Millsap, who totaled just 26 points in the first three games of the series before erupting.

Stevens said, “Obviously, you’re throwing darts a little bit with a guy that’s rolling like that.”

Said Smart, who is 4 inches shorter and 40 pounds lighter than Millsap: “Just (tried) to really stop and make it hard for him, pressure him and really contest every shot that he took.”

Stevens added, “When you’ve scored 45 through three quarters, you probably are a little winded.”

Millsap said, “I blame myself for not being aggressive down the stretch and not putting the ball in the hole.”

Johnson scored Boston’s first five points of overtime, and Isaiah Thomas (team-high 28 points) nailed a 3-pointer from the right corner to ice the game with 30 seconds left.