The Heat won Game 2 by 19, lost Game 3 by 36 and then cruised to a 16-point win in Game 4 on Thursday night to even things up. This series may be on a run of blowouts, but each game was close at halftime and felt like it could have gone either way until one or two factors conspired to bring on the avalanche.

“This series is being decided by this,” Heat Coach Erik Spoelstra said, pinching his index finger and thumb together. “It might not be that way in the (scores), but in terms of how competitive it actually is.”

It’s a three-game series now with a pivotal Game 5 on Sunday in San Antonio.

“It’s a play here, a shot here or there with three minutes to go or could be a period at the end of the third period where you turn it over two or three times and the other team makes two shots,” Spurs Coach Gregg Popovich said. “It could be a call or a turnover. Very, very fine line.”

With that in mind, here’s a look at some of the keys and the obstacles for both teams.

WHY THE HEAT CAN WIN

• They’ve got the best player in the world in LeBron James and he’s finally playing like it. In Game 4 he looked like the four-time MVP: 33 points, 11 rebounds and four assists.

• They don’t have to win on the road again: The Heat’s victory Thursday assured them that the series will end on South Beach, where Games 6 and 7 are scheduled to be played.

• Spoelstra’s gamble to insert sharp-shooter Mike Miller into the lineup worked like a charm. Miller didn’t score a point in Game 4 but his mere presence forced Popovich to abandon his best defensive lineup.

WHY THE HEAT ARE IN TROUBLE

• Dwyane Wade’s health: He was brilliant in Game 4 with 32 points and six steals, but will his aching knee allow him to sustain that effort?

• Inconsistency: The Heat haven’t won two straight games in about three weeks.

• They’re not as intimidating: The Pacers took them to seven games and the Spurs have not backed down.

WHY THE SPURS CAN WIN

• Game 5 is in San Antonio: The Spurs have the early advantage in this best-of-three by getting the first one at home. It’s a crucial one for them so they don’t have to go to Miami needing to win two straight.

• They have already won in Miami: Winning Game 1 last week gives the Spurs the confidence in South Beach.

• They have had success against LeBron: Prior to Game 4, the reigning MVP was completely flummoxed by the paint-clogging Spurs defense.

WHY THE SPURS ARE IN TROUBLE

• Manu Ginobili has disappeared: He is averaging just 7.5 points in the series.

• Tony Parker’s health: The point guard has been slowed by a strained right hamstring that he said “could tear any time now.” If so, the Spurs are sunk.

• They’ve been sloppy: Since tying a finals record for fewest turnovers in Game 1, the Spurs have given it up 47 times.