Doc Rivers has done the X’s and O’s, and factored in intangibles and unpredictability. Now he wants the Celtics to do the math.

“We have one home game left, and that’s it in this series,” Rivers said during a conference call Wednesday. “We have to understand that and come with that sense of urgency.

“I think our guys get that. And you know what? So does Miami.”

The Celtics have gained the upper hand in the Eastern Conference finals, overcoming the odds with a 94-90 win over the Heat Tuesday. The victory, the Celtics’ third on the road in the postseason, gives them a chance to close out the series in Game 6 at TD Garden Thursday night.

One more victory and the Celtics would make their third trip to the NBA Finals in five seasons. And this would be one of the most improbable advancements in franchise history, as the Celtics had a losing record halfway through the season.

Rivers’s coaching strategies and ability to manage substitutions and motivate players have made a difference throughout the playoffs. His faith in Mickael Pietrus paid off in Game 5 as Pietrus found his shooting touch and also improved the team’s athleticism and quickness defensively, plus its ability to react in improvised situations.

As Heat guard Dwyane Wade noted after the contest, “They beat us to the 50-50 balls, and that was the difference.”

The Celtics were not winning those battles early in the series. But that changed Tuesday. When the intensity increased and the margin for error decreased in the final minutes, the Celtics were able to not only calmly execute out of timeouts, but also respond spontaneously to Miami’s sometimes spectacular shotmaking and shot-blocking.

Examples included Rajon Rondo’s rebound-assist for a Pietrus 3-pointer, following a Wade block on a Brandon Bass dunk attempt; and two Paul Pierce free throws just five seconds after a successful Wade drive, the Celtics turning a Miami make into transition points.

Rivers downplayed the tactical tweaks, but he has been able to optimize the effect of what he considers “little” changes, which he believes cause opponents to make “big changes.”

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