The Boston Celtics could close out their first-round playoff series on Friday night in Chicago.

Holding a 3-2 lead in the best-of-seven series over the Bulls, the Celtics have won their first two games in Chicago and the Bulls will once again be without injured point guard Rajon Rondo.

But, win or lose, Friday night will be a somber affair for Boston star Isaiah Thomas, who has been grieving the recent loss of his younger sister.

After the game, Thomas will fly back to his home state of Washington to be with his family, according to ESPN.com sources. He said to reporters earlier this week that keeping his focus on the court during these trying times has been a struggle:

"Man, I'm just taking it day by day. Some days are better than others," Thomas said Tuesday. "I'm not here, man. It's never going to be the same."

Though he may seem like his old self when he's on the court, it's clear that his time playing the sport he loves has served as a therapeutic release. Being surrounded by his teammates makes things temporarily easier by taking his mind off of what he's dealing with off the court.

Fellow guard Avery Bradley, one of Thomas's closest friends on the team, told ESPN after Game 5 that the Celtics are trying to rally behind their star and have experience doing just that after dealing with (admittedly lesser) adversity for most of the season:

"I mean, it’s kinda been the story of our team, being able to fight through adversity. No matter what we go through, we would overcome it," Bradley said. "And I think it’s a group of guys, our coaching staff, we believe. We believe in one another."

Bradley and Thomas each scored 24 points in Boston's 108-97 Game 5 victory. Bradley also played lockdown defense on Bulls star Jimmy Butler, who scored only 14 points after exploding for 33 points in Game 4.

If Bradley can turn in another effort like that on Friday night, the Celtics close out the first-round series and advance to the Eastern Conference semifinals, where they'd face the winner of the series between the Washington Wizards and Atlanta Hawks (which the Wizards lead 3-2).

Going back to Tacoma for his sister's funeral with a first-round victory certainly wouldn't make the grieving process easier, but it would give Thomas more time to be with his family. If the Celtics can't eliminate the Bulls on Friday night, Game 7 would be held at 1 p.m. Eastern time back in Boston.