Heat coach Pat Riley wasn't bluffing. Insisting something had to be done about his team's ragged starts, Riley shook up his starting lineup Monday.

Out at small forward was Kendall Gill, who had started the previous 33 games. In for the opening tip against the Celtics at AmericanAirlines Arena was Jim Jackson, who had started 17 games earlier in the season.

It was the first time Riley had altered his starting lineup for any reason other than injury since Jan. 15, the date Gill replaced Jackson for a road victory against the Lakers.

"It's concerning to me why we can't come out and muster up the intensity and attitude that we need to jump on somebody, not depend on me having to search for something to get it going," Riley said.

With Gill starting alongside center Alonzo Mourning, power forward Brian Grant and guards Eddie Jones and Rod Strickland, the Heat had gone 21-10.

The Heat went into Monday's game 6-11 when starting Jackson alongside Mourning, Grant, Jones and Strickland.

The Heat blew out to a 14-4 lead against the Celtics and led 21-14 after the opening period, the first time in four games it took a lead into the second quarter. It had been outscored in the first quarter of its previous three games by an average of 23-17.

Considering the Heat has only 13 games remaining, it seemed an unlikely time for a lineup shuffle. Riley, however, said he had no choice.

"It hasn't been a problem until the last week," he said. "We've got to get our starters thinking the right way. There's a huge difference between playing and coming to really fight for something."

Gill had been a marginal starter in recent games. Entering Monday's game, he had not played more than 17 minutes in any of the previous four games, used for only 11 minutes in Saturday's loss in San Antonio.

With Jackson in the starting lineup, Riley was able to use LaPhonso Ellis as his first perimeter reserve off the bench. Ellis had played only eight minutes in the previous four games since returning from the injured list.