WALTHAM, Mass. -- Boston Celtics point guard Isaiah Thomas spent the past year texting new friends such as New England Patriots quarterback Tom Brady and Los Angeles Lakers legend Kobe Bryant with a moment like this in mind. He has questioned boxer Floyd Mayweather and Philadelphia 76ers legend Allen Iverson about a situation like this.

Thomas has been relentlessly motivated by a goal of proving he can lead a team to victory in the postseason. He has peppered some of pro sports' biggest names on how to thrive on the biggest stages. So even as he muscled his 5-foot-9 frame into the MVP conversation this season, Thomas was the first to admit that, after a pair of first-round exits for the Celtics the past two seasons, he didn't know what it took to win in the playoffs.

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Now, despite a first-round victory already on his résumé this season, Thomas yearns for more. The Celtics are two wins away from a trip to the Eastern Conference finals, and, on the eve of a potentially pivotal Game 5 against the Washington Wizards, Thomas embraced a suggestion that this might be the most important game of his six-year NBA career.

"I'm treating it as a must-win," he said. "I'm treating it as the biggest game that I've ever played. Hopefully, everybody else is treating it like that."

Spectacular in the first two games of this semifinal series, Thomas struggled mightily in Games 3 and 4 in Washington, both of which the Celtics lost. After being limited to two second-half points and no free throw attempts in Sunday's Game 4, Thomas fumed about a lack of whistles and the way the Wizards were allowed to "hold and grab" him.

Thomas hasn't backed down from that assertion, but he has also noted that, regardless of how the referees call the series moving forward, he has to better impose his will on Wednesday's game.

"I know I gotta play with my foot on the gas. I can't take it off," he said. "I gotta keep going, and I know if I do that, my teammates will follow. I'll be ready for [Game 5]."

Two days off before Games 4 and 5 have forced Thomas to marinate on his struggles and those of the Celtics as a whole. After superhuman efforts during wins in Games 1 and 2, in which he averaged 43 points on 51.8 percent shooting, Thomas has averaged just 16 points on 45.5 percent shooting the past two games. He had never scored fewer than 20 points in consecutive postseason games before the previous two tilts.

The Wizards have done everything they can to disrupt Thomas -- blitzing pick-and-rolls and clogging the paint with multiple bodies -- and Thomas' sloppy play, reacting poorly to the increased attention, contributed to Boston's unraveling while the Wizards went on a 26-0 run in Game 4.

Isaiah Thomas averaged 43 points in Games 1 and 2 but has averaged just 16 points in the past two games. Maddie Meyer/Getty Images

Celtics coach Brad Stevens has spent much of the past two days talking about a need to space the floor better and counteract some of Washington's length, which has made it tough for Thomas to find room to operate. It's fair to wonder if Stevens might again tinker with his lineup and rotation, maybe leaning more heavily on floor-stretching big man Kelly Olynyk to help space the floor without sacrificing size. Olynyk and rookie Jaylen Brown were in green starter jerseys at the end of practice Tuesday, while Amir Johnson was back in reserve white. Stevens said he'll wait to announce his starters for Game 5.

"I don't think Isaiah feels any pressure, but I think it's just a team effort," Olynyk said. "We've got to be able to space the floor and make shots like we have in the regular season. If they're going to load up on Isaiah and put two, three guys toward him and all the attention on him, we've got to get the ball out of his hands quickly and move it to the next open guy, and hopefully we can come back to him later in the clock."

Thomas became too careless with the ball in the third quarter of Game 4, and his five turnovers were a big reason the Wizards were able to get in transition and create easy points. Stevens has again stressed to his team the importance of forcing Washington to operate in half-court sets.

The Wizards ranked third among all NBA teams while averaging 1.189 points per play in transition during the regular season, according to Synergy Sports data. That number dove to 0.952 points per play when forced to play in the half court against a set defense, ranking 13th overall.

Celtics players have acknowledged that preventing turnovers could go a long way toward fixing the issues in D.C.

"I think a lot of times it's turnovers and transition, and they've done a good job of really using their length and athleticism to impact us, especially in the past two games in those runs," said Stevens, whose team also gave up a 22-0 run in the first quarter of Game 3. "I felt like we were lucky to be up 2-0 when we left Boston, and now, as poorly as we played in the last two, we're still 2-2, so our focus is on how we can play better. We've spent a lot of times the last two days talking about that, and I think everybody wants to put their best foot forward."

Thomas' size 12 shoe must lead that way.

"We just gotta focus in, we gotta lock in," Thomas said. "We gotta remain confident in ourselves and know what we did to get us to this point. Everybody has to continue to remain confident.

"It's going to be a big game. We're ready for it, though. I'm ready as can be."