LeBron James faces another Game 5 against the Boston Celtics. (Getty Images)

Previewing Game 5 between the Miami Heat and the Boston Celtics in the Eastern Conference finals. 

1. Where We're At: The series is tied at two games apiece after both the Heat and the Celtics held serve at homecourt. Already through four games, it's been an unpredictable series, with one dominant Miami victory, one solid Boston victory and two overtime games that could have gone either way. The series could see another major injection of surprise on Tuesday, as Heat All-Star forward Chris Bosh could reportedly make his return after being sidelined for three weeks and nine games with an abdominal strain. The Heat looks to hold homecourt and get the third win that eluded them in Boston. The Celtics look to steal the road win they almost had in a Game 2 overtime loss and head home with a chance to close out the series update at TD Garden on Thursday night.

2. The Big Number: 8.5. That's the average halftime deficit for the Heat, who trailed at the half by double digits in Games 3 and 4 and have yet to hold a halftime lead in the series. Miami has used two different starting lineups as they try to make up for Bosh's absence so that's part of it. Guard Dwyane Wade has been a factor here too, as he let his offense come to him in Games 1 and 2 while strugging with Boston's pressure in Games 3 and 4. The Heat's second unit has also played much better, at least offensively, in the second halves of this series so far, with long first half droughts during both games at TD Garden. The Heat have shown plenty of fight in launching multiple major comebacks but surely coach Erik Spoelstra wouldn't mind playing from ahead at some point.

3. Key Adjustment: If Bosh plays, everything changes. CBSSports.com's Matt Moore breaks down the effects of his return on both sides of the ball. At Tuesday shootaround, Wade said he was looking forward to Bosh keeping Celtics forward Kevin Garnett honest on defense, as Garnett has been able to avoid the likes of Ronny Turiaf and Joel Anthony to concentrate on filling the paint and protecting the rim by playing aggressive weakside defense. In addition to that ability to space the floor, Bosh is a fine passer from the high post and will alleviate some of the ball-handling and play-initating pressure from Wade and LeBron James. On the other end, the Heat can really use his length on defense and his rebounding ability and the opportunity to match-up James with smaller players is always an advantage. The Heat remain cryptic on whether Bosh will actually take the court in Game 5 but all indications, from both sides, seem to be that his return is expected because he has participated in multiple basketball workouts and went through shootaround with the team on Tuesday morning.

4. The Big Story: LeBron James vs. the Boston Celtics in Game 5. Any time those words get used in the same sentence, the mind drifts back to 2010, when James rolled over against the Celtics during his final game at Quicken Loans Arena as a member of the Cleveland Cavaliers. This time, there's no talk of an injured elbow, no salacious off-court rumors and no free agency waiting in the summer. Totally different circumstances, really, but a loss here -- as the favorite, at home and with an NBA Finals berth at stake over the next five days -- would still be pretty devastating. James vowed on Tuesday to "play his game" after fouling out of a Game 4 loss on Sunday, the first time he had fouled out of a playoff game during his career. His play has been consistently extraordinary throughout the series; anything less on Tuesday would qualify as a major surprise.

5. The Facts: 8:30 p.m. ET tipoff on Tuesday at AmericanAirlines Arena. Ray Allen (ankle) will play after chatter earlier in the series that he might need some time off. Chris Bosh (abdominal strain) is listed as a "game time decision" and is reportedly expected to play for the first time in three weeks.