The Celtics, in the wake of their 105-99 loss to San Antonio, have dropped two straight home games for the first time since the 2006-07 season. The Celtics, 4-0 against the Spurs and Lakers last regular season, now are 0-3 against both in 2008-09 with a March 20 game in San Antonio left to play.

They also are 1-4 against the Lakers, Cavaliers and Spurs combined. In Final Four terms, they aren't getting past the Saturday game. Not with the way they currently are finishing - or more correctly, not finishing - their work.

``It was one of those games where the first team to play a little bit of defense was going to win,'' said Paul Pierce, identifying yesterday's most obvious deficiency.

Two of the best defensive teams in the NBA - as coach Doc Rivers referred to both sides - shot a little too well for comfort against each other.

The Spurs finished the game at a 48.8 percent clip, and dropped two huge quarters on the Celtics, including a 38-point second and a 31-point fourth.

The Celtics shot 50.6 percent and, according to Rivers, ``When we shoot 50 percent, we should win.''

Not like this, they won't.

The Celtics held a 93-90 lead with 1:36 left and were upended when the Spurs scored 11 points in the next 30 seconds, in addition to outscoring the Celtics 15-6 over the last 45 seconds. San Antonio's last 10 points came from the line, with the Celtics attempting to buy time with fouls against a team that shot 10-of-11 over the last 20 seconds.

``That's San Antonio,'' Kendrick Perkins said. ``They've been here for the last eight or nine years or whatever. They're a consistent championship-style team that plays together, that's well-coached and has great leadership by their captains.

``They had six days' rest, and they came in and showed what they can do. You've gotta share the ball, and I don't think we did that tonight.''

Indeed, Rivers singled out one six-minute stretch in the fourth quarter when the ball never moved.

``Whoever had it shot it. I thought our guys felt each other being tired and thought, `I'm going to win it for us tonight,' '' he said. ``Usually when you do that, you lose it.''

That stretch also negated a superlative second-half opening, when the Celtics scored on their first four possessions and opened up a 64-60 lead with a 12-0 run.

San Antonio absorbed the punch and hit back.

The Celtics, however, appeared to be in control down the stretch with a 10-3 run that was interrupted only by Tim Duncan's three-point play off a put-back. Kevin Garnett, who had six points in the burst, rimmed out an open 15-footer two possessions later, and the game went south.

Roger Mason took the lead back (95-93) on a 3-pointer with 20 seconds left. Manu Ginobili then practically grabbed a sideline pass out of the hands of inbounder Ray Allen.

Pierce was forced to grab Ginobili, who was awarded two free throws off a clear path foul call. He hit both for a 97-93 lead, and then hit two more after the Spurs retained possession in a brutal four-point swing.

Pierce badly missed a 3-point attempt, Eddie House booted the rebound out of bounds, and the purposely fouled Mason hit two for a 101-93 lead with 14.9 seconds left.

``Homecourt's not going to win games for you,'' Rivers said. ``You have to actually play. I thought we had the right mind-set. We just didn't play well.''

- mrmurphy@bostonherald.com