CHICAGO -- The day before the Boston Celtics played their regular-season finale, the team went through a light, split-squad workout. But there was something about the intensity that veteran Gerald Green displayed in an otherwise unremarkable off-day session that stuck with head coach Brad Stevens.

The next night against the Milwaukee Bucks, after the Celtics fell behind in a game they needed to win to ensure the No. 1 seed in the Eastern Conference, Stevens deployed Green early, and his offensive spark helped Boston rally and race away with a victory.

"You just had a feeling like, here's a guy that's a little bit older, we know what we can do on offense, but he had a little bounce in his step," Stevens said after that win over the Bucks. "Gerald is a perfect example of a guy that could really help you. So I'm excited about the way he played, but I'm just as excited about his consistency and his work. ... Those things kinda stick with you."

It must have stuck with Stevens into the postseason. Fast-forward nine days after that victory over the Bucks and, after Boston dropped the first two games of its first-round series against the eighth-seeded Chicago Bulls, Stevens raised eyebrows when he elected to move Green into a small-ball starting lineup for Friday's Game 3.

In the biggest game of Boston's season, Stevens elected to lean on a player who had logged 29 DNPs this season, including one in Boston's Game 2 loss in which Stevens played 11 of the team's 13 active players. Stevens decided to roll the dice with a player who hadn't started a game for the Celtics since April 13, 2007.

Boston responded by playing its most inspired ball of the postseason as part of a 104-87 triumph and now has the chance to even the series during Sunday night's Game 4 in Chicago.

Green chipped in eight points on 3-of-8 shooting and was plus-5 -- meaning the Celtics outscored the Bulls by five during his 20 minutes of floor time in Game 3. His presence in the starting lineup wasn't the biggest reason that Boston played better, but Green absolutely helped open up the floor, and his energy was palpable, both when he was on the court and when he offered encouragement to teammates on the sideline.

"I was just trying to bring energy. I think that was most important," Green said. "I feel like my energy was there early on in the game. So that’s what I’m going to try to do [in Sunday's Game 4]: just try to come out with a lot of energy and just try to play up-tempo basketball, try to just bring it on both ends."

The excitable Green admitted it doesn't take much to get him going.

"I kind of like being geeked up. I think that’s the type of personality I have anyway. I’m always animated; I’m always kind of crunk," Green said. "I gotta bring that energy. I don’t want to be less geeked than I was. Obviously, I don’t want to be too emotional. I just kind of want to use my energy on the court so I can just be able to be effective on both ends of the floor."

That Green has elevated to a starting role in the postseason is still a bit jarring. At age 31, Green is the oldest player on a Celtics roster that skews young. He is 12 years, seven NBA teams and two continents removed from when Boston drafted him out of high school with the 18th pick in the 2005 draft.

Green signed a one-year, veteran-minimum deal with the Celtics this past summer. Even before the season, some wondered if Green's roster spot might be better utilized to carry one of Boston's surplus of recent draft picks, but Green stuck on the final roster (and James Young ultimately beat out R.J. Hunter for the final spot). Whenever Stevens desired an offensive jolt during the regular season, he would dust off Green.

But few expected to see much of Green in the postseason, especially not in a starting role. But Stevens suggested Saturday that his plan is to keep Green with the first unit for Game 4, which is understandable after the Celtics' starters were plus-13 in 15 minutes of floor time Friday night.

"Adding Gerald to the starting lineup definitely helped us out a lot," said Celtics guard Avery Bradley. "It added someone that not only is willing to shoot, but that’s a capable shooter and a capable playmaker for our team."

Added Al Horford: "We hadn’t played with Gerald much this year. But credit to him, he was ready to go, and he was great for us."

Stevens could have easily gone with Jonas Jerebko in the starting lineup -- especially considering Jerebko was a starter last postseason -- and likely experienced similar results. Both Green and Jerebko can provide shooting and energy. Jerebko ended up giving the team a lift off the bench in the second half, helping Boston stretch out its lead even when Isaiah Thomas was off the floor.

The bottom line for Boston was a much-needed victory for a team that had a cloud hovering over it since the death of Thomas' sister last weekend. Green said he believed the mood in the locker room shifted after Friday's victory.

"Everybody knows what type of ... week it’s been for [Thomas]. But it was good to see him in good spirits," Green said. "And it changed the atmosphere of the locker room. As a leader, I think he understood that. But I think everybody, at the end of the day, had his back regardless of what or how he was feeling. So I was glad to see him up and live and cheering guys on."

Added Stevens: "This is a tough week. And it was good to see our guys feel good about themselves because I thought they certainly deserved to feel good about themselves, and it was good to play a little bit better."

Both Stevens and Green cautioned that Game 4 won't come any easier because of Boston's Game 3 success. The Celtics expect the Bulls to play better, and Green said the Celtics must elevate their play.

Green has emerged as a strong voice on this Boston team. He joked before the season about how odd it was to have once been a teenager and the youngest player on the Celtics roster, but now the oldest. He's embraced that leadership role by being increasingly vocal with teammates, including close friend Thomas, whose presence was one of the primary reasons Green signed with Boston last summer.

Even though Boston's younger players often tease him for his advanced age, Green still has springs in his legs and often wows teammates with glimpses of the hops that made him a dunk champion. Stevens has often referenced Green's ability to score in spurts and maintained that he would eventually help Boston in key spots this season.

Few expected it would come on the playoff stage.