What was once a seven-game lead in the Western Conference has shrunk to 2 1/2 games, while the Spurs are mired in a five-game losing streak and the Lakers are closing fast.

The first four games of the Spurs’ losing streak were easy to rationalize. They all came with Duncan out with a sprained left ankle. One came with four starters out. Three came on the road.  All of them were close. Thursday, with Duncan back and the Big Three whole, there were no excuses.

The Spurs had hoped to use Thursday’s game as a chance to jump-start their stretch run. Instead it was Boston, who have been also been struggling through a March, that found rejuvenation.

“This is about the worst time it could happen, at the very end of the year,” coach Gregg Popovich said. “You’d rather have it happen 30 games ago, where you have time to get back and recover. We’ve got to step on it a bit.”