This was nearly the defining win of the season.

After mostly losses, and a few victories over mediocre teams, on Thursday night at the Wells Fargo Center, the 76ers had all but defeated the Boston Celtics.

But, as is often the case against such league leaders, the Celtics made a flurry of plays down the stretch: a three-pointer by Ray Allen; a midrange jumper by Glen Davis; and, finally, an over-the-top lob to Kevin Garnett.

Garnett's bucket was the game's last, banked in with 1.4 seconds on the clock.

At the end, the Celtics defeated the Sixers, 102-101.

Without another time-out, the Sixers could only attempt a long inbounds pass from under Boston's basket. Garnett picked it off.

The Sixers dropped to 7-15. The Celtics, led by Allen's 23 points, improved to 18-4.

The Sixers' streak of five consecutive home victories ended despite a swooping, driving layup by swingman Andre Iguodala with 6.6 seconds left in the game.

The basket, Iguodala's second in the final 42.1 seconds, gave the Sixers a 101-100 lead.

In the third quarter, the Sixers looked like they were cruising toward the win, this game in their palm. With 2 minutes, 39 seconds left in the period, the Sixers were ahead, 80-72. The lead ballooned to its highest on a couple of free throws by guard Lou Williams, right before that same lead deflated under a 9-0 Celtics run.

Boston's burst ended with a dead-on, banked three-pointer by Rajon Rondo, the Celtics' point guard, with les than a second left in the third quarter.

Entering the fourth, the Sixers trailed, 81-80.

For the Sixers to compete with the Celtics, they were going to have to make outside shots, rebound, hold the Celtics to a low shooting percentage, and stay focused through all Boston's spurts.

And in the first half, that's almost exactly what happened.

The Celtics managed to shoot well enough to win almost any game, making 58.3 percent of their shots in the first half but were outrebounded and outshot from both the field and the free-throw line.

The Sixers finished the first half with 21 rebounds, six more than Boston. The Sixers made 12 first-half free throws, two more than Boston. And the Sixers took 42 first-half field-goal attempts, six more than Boston.

But it was the Sixers' we-can-win mentality that kept them even with the Celtics. Inside a Wells Fargo Center that had more filled seats than most home games, the Sixers seemed not at all afraid of the Eastern Conference's best team.

On the final possession of the first half, Boston's all-star point guard, Rondo, held the ball near half-court. Rondo, waiting for the clock to tick down before starting his attack, looked at the guy guarding him and smiled.

It was Sixers shooting guard Jodie Meeks, a fellow attendee of the University of Kentucky.

Rondo held the ball high, crouched low in his stance. Meeks seemed to inch closer. With about six seconds left in the half, Rondo began his attack toward the top of the key and then just off the right elbow. He hesitated, unable to shake Meeks, and settled for a difficult scooped layup just a few seconds before the halftime buzzer. He missed, and the Celtics led by 56-55 at the break.

At no point in the first half, not when Allen was hitting a three-pointer or when Nate Robinson was making a trio of treys, did the Sixers seem anything but focused on winning the game.

Contact staff writer Kate Fagan at 856-779-3844 or kfagan@phillynews.com.