Earlier this season -- before he became a sensation and the huge blinking neon X-factor for the Celtics in their unlikely final run -- Avery Bradley threw a diagonal cross-court pass to Keyon Dooling behind the 3-point line in transition. Asked afterward if he would have dared make that pass last season, Bradley’s eyes grew wide and he shook his head.

No way.

It’s been quite a ride for the 21-year-old who began the season with no defined role and few expectations. Then in January he subbed for Rajon Rondo at point guard after Rondo hurt his wrist. The Celtics went 6-2 in those games with Paul Pierce playing point-forward, but Bradley took care of the ball and was able to unleash his defensive prowess on an unsuspecting league.

It wasn’t long before his veteran teammates were telling anyone who would listen that Bradley was the best on-the-ball, full-court defender in basketball. That was just a prelude to much larger contributions that have taken place in the last third of the season, but that experience was invaluable for a young player, considering Bradley had trouble even staying on the court as a rookie.

The NBA gives out an award for “Most Improved Player,” and there’s no reason Bradley shouldn’t be at the top of the list. The problem with the award is the definition is rather nebulous.

Depending on one’s perspective, players like James Harden and Ryan Anderson could be considered for the honor in that they have gone from steady contributors to featured performers. Jeremy Lin is an obvious candidate. He went from one foot out of the league to magazine covers, but his rise had to do with opportunity as much as improvement. Then there’s Minnesota’s Nikola Pekovic, who went from lumbering foul-prone oaf to menacing, and quite skilled, sidekick for Kevin Love. 

Bradley’s rise is no less remarkable. He played only 162 undistinguished minutes last season as a rookie. He took 67 shots, missed 44 of them and scored almost half his points in a 20-point outburst on the season’s final day in a glorified exhibition against the Knicks. He had more turnovers (16) than assists (12) and a Player Efficiency Rating (PER) of 2.2.

In his second season, Bradley has played more than 1,200 minutes and is shooting better than 50 percent from the floor and 44 percent from 3-point range. His defense has been otherworldly at times and since his surprise insertion into the starting lineup on March 25, the Celtics had gone 12-5 and moved from the back of the pack in the Eastern Conference playoff race to the top of the Atlantic Division.

They are more than five points tougher on defense when Bradley is on the court than when he’s off and the new-look starting lineup is a rather absurd 18.72 points better than the opposition per 100 possessions. His backdoor cuts have become a prominent feature of their offensive sets – something he developed during the year -- and his suddenly reliable 3-point shooting has been nothing short of a revelation. (Since replacing Ray Allen as a starter, Bradley has made 18-of-30 shots from behind the arc).

“What you see is a product of a young guy being around our system and gaining confidence within that,” Kevin Garnett said. “Not just from Doc Rivers and the coaching staff but to be able to gain confidence with his teammates and within himself. He’s playing with a high confidence right now. We’re loving it. We’re feeling it.”

In what could have been a tricky, awkward situation with Bradley replacing a Hall of Fame veteran, he has seamlessly made the transition to starter and he’s done it in a way that his veteran teammates respect. 

“Love seeing young guys who work hard and it pays off,” Garnett said. “Love young guys who listen and put in the hard work. Seeing where he’s come from to where he’s at now is just beautiful, man. I hope they reward him with some longevity and something long-term.”

Bradley is a few years away from a long-term deal, but he has gone from question mark to future cornerstone for the Celtics’ long-term rebuilding project. There are valid arguments to be made for others players as “most improved,” but has anyone made as big a leap as Bradley?

The Hawks and homecourt

Doc Rivers told people a month ago that if it came down to seeding, homecourt or any other playoff positioning he was going to choose rest and health.

“At the end of the day if it comes down to seeding or health, I’m going to choose health,” the coach said in late March. “You would rather have a better seed but you can go wherever you want, if you’re not healthy it’s not going to matter, especially with us.”

Rivers raised some eyebrows around the league when he held Pierce and Garnett out of their game Friday against the Hawks. They joined Rajon Rondo (back), Ray Allen (ankle) and Mickael Pietrus (knee) on the sidelines and the shorthanded C’s dropped a game and a half behind Atlanta for homecourt advantage with a 97-92 loss on Friday night.

Adding another layer to the decision was the fact that Rivers played Pierce and Garnett against Orlando on Wednesday, and the Celtics’ victory that more or less knocked the Magic out of contention for the fifth seed. This may have backfired when it was learned later that center Dwight Howard would undergo back surgery and be out for the rest of the season and the playoffs.

Wouldn’t a depleted Magic squad be a more enticing first round opponent than Atlanta? Possibly, but the Howard announcement came after Wednesday’s game and if there’s one thing the Celtics want to avoid in the playoffs it’s a matchup with one of the (few) elite centers.

The Hawks are also dealing with a key injury as Al Horford tries to work his way back from surgery to repair a torn pectoral muscle. Horford said he was “frustrated” by his lack of progress after a workout last week and coach Larry Drew said the team has been preparing as if they won’t have their All-Star big man in the postseason.

Ultimately, Rivers chose rest and health over seeding as he said he would, and time will tell if it was the right decision.

Taking a chance on talent

There’s no doubt that Sean Williams, the former Boston College star, has talent. As a rookie with the Nets in 2007-08, Williams averaged 11.5 points, nine rebounds and three blocks per 36 minutes. But he has appeared in just 61 NBA games over the last four seasons and was out of the league entirely in 2010-11.

After bouncing around the international scene and the D-League, Williams appeared in eight games for the Mavericks who released him on March 22, making him eligible for the postseason roster.

At this point in the season, Williams is an insurance policy. The Celtics are set up front with Garnett, Brandon Bass and Greg Stiemsma, but considering age, health, Stiemsma’s foul-prone tendencies and Ryan Hollins’ lack of production, adding another big was necessary.

To make room for Williams, the team released center Jermaine O’Neal, officially closing the door on an enigmatic two seasons. O’Neal had his moments, but he was never able to provide the consistent presence they thought they were getting when they signed him for the full mid-level exception after the 2010 season.

If nothing else, Williams provides an extra big body for a roster that needs one. The cost is minimal and the expectations are even less.