After a fifth straight Celtics loss, his team searching for answers on offense that he hasn't supplied, Jason Terry left swiftly, straight-faced, pushing his way through a sea of reporters waiting to enter the victorious Knicks locker room. While the leprechaun tattoo remains, gone are his confident smile and championship guarantees.

If Paul Pierce is struggling, then Terry is lost. After averaging 11.6 points (44 FG%, 38 3P%) in 31 minutes a night through December, the 35-year-old's production nosedived to 5.6 points (38 FG%, 26 3P%) in 21 minutes a game this month. This comes after Avery Bradley's return and Terry's subsequent move to the bench, where he's been a perennial Sixth Man of the Year candidate. To say he's been a disappointment is an understatement.

This isn't the same guy who scored 15.1 points off the bench every night and raised that production in the clutch to 28.3 points per 36 minutes during the Mavericks' run to the 2011 NBA championship. And this definitely isn't the guy who was supposed to offset the loss of Ray Allen's 14.2 points (45.8 FG%, 45.3 3P%) per game last season.

Where did that Jason Terry go? And, more importantly, can the woeful Celtics offense find him before the first -- and most important -- season of his three-year, $15 million contract comes to a close?

"It takes time," said Knicks point guard Jason Kidd, Terry's backcourt mate for four-plus seasons in Dallas. "He's in a new system, and a lot of things aren't run for him like they were in Dallas, so he's just making that adjustment. He's a professional, he's good at what he does, and so it's just a matter of time before he starts making every shot."

Bradley's return and Courtney Lee's struggles were supposed to finally carve out a familiar role for Terry, but it's been just the opposite since his move to the bench. It's hard to find a worse three-game stretch over Terry's career than his past three outings (10 points, 4-14 FG), so Celtics coach Doc Rivers has turned to Lee's defense and Leandro Barbosa's explosive offense to fill the void left by Terry's anemic performance.

"Sometimes, it takes a while, especially for a guy like JET, who's a rhythm player," said Knicks center Tyson Chandler, who also won a ring with Terry on the Mavericks. "He was in a situation and a system [in Dallas] where he understood exactly what he had to come out and do."

There's the rub. It wasn't just that Terry came off the bench, it's how the Mavericks used him in their offense. During that 2011 title run, only a third (4.3) of Terry's 13.3 shots per night came from 3-point range; as for the other two-thirds of his buckets, he created more than half of them (50.6 percent) by himself. On the Celtics, he takes half (4.2) of his 8.5 shots from beyond the arc, and almost 80 percent of his field goals (78.0 percent) come from assists.

"It's just a whole different scheme here," added Kidd. "Him and Dirk [Nowitzki] were our offense [in Dallas], but [the Celtics] have got a lot of guys that they can go to, so it's just him getting comfortable."

While Terry ranks fourth behind only Allen, Reggie Miller and Kidd among 3-point shooters in NBA history, the 6-foot-2, 180-pound scorer might be most comfortable in the mid-range, where he consistently ranked among the league's best shooters in Dallas. In 2011, he attempted almost half of his shots (45 percent) from 10-23 feet and created half of those himself. This season, he only takes a third of his shots from that distance, and a whopping 90 percent of those came from assists. In other words, the Celtics are trying to turn Jason Terry into Ray Allen.

"JET is an incredible player," said Chandler. "He's a clutch player, and he's a clutch moment player. He just has to get in a rhythm here, and they have to find a way to get him in a rhythm."

In Boston, Terry's production actually declines from 12.5 points (42 FG%, 35 3P%) per 36 minutes to 9.7 points (32 FG%, 23 3P%) in the clutch. So, how does Celtics coach Doc Rivers, whose team is averaging only 86.0 points in regulation over this five-game losing streak, help Terry find his flow?

"He came in exactly at a certain part of the game in the first quarter," added Chandler, fresh off making his first NBA All-Star roster, "he got right into his sets, he was a great 1-2 punch with Dirk, he finished every game, so having that kind of responsibility and now just being a stretch-the-defense kind of guy in the corner and getting set here and there, that's not what he was accustomed to. It could take some time."

Just as Rivers structures Kevin Garnett's playing time, Mavericks coach Rick Carlisle consistently managed Terry's 30-plus minutes a night. He inserted his second-leading scorer midway through the first and third quarters, and after a brief rest during the second and fourth quarters, Carlisle closed each half with Terry on the floor. That system seemed to pay dividends for Terry, including his Sixth Man of the Year trophy in 2009.

As Chandler said, "If you go back and look at the [2011] finals, JET took over that Game 6."

With that 27-point performance, he came through on a championship guarantee that came in the form of a Larry O'Brien trophy tattoo on his bicep. Before their title hopes slip away, the Celtics need to find that Jason Terry again.