BOSTON (TNS) — The Eastern Conference finals had been reduced to a best-of-three series, but Cavaliers star LeBron James didn't look at it that way hours before.

"Nah, it's a best-of-one series," James said.

Wednesday night's Game 5 at TD Garden had all of that urgency, all of that scrappiness, all of that smothering defense. The Cavs' Larry Nance Jr. may have the scratches to prove it.

But after the Boston Celtics ran off with a convincing 96-83 victory and improved to 10-0 at home in the postseason, it is a best-of-one series. The Cavs must stave off elimination in Friday night's Game 6 at Quicken Loans Arena.

Facing the end of a James-led run that includes three consecutive trips to the NBA Finals and perhaps the end of an era if James departs again in free agency, the Cavs slipped back into familiar, destructive habits.

James' supporting cast, save for Kevin Love, was of little help. In the first quarter, only James and Love made field goals as the Cavs once again showed they don't have enough firepower.

After averaging 14.8 turnovers in the previous four games and committing a series-high 19 in Game 4, the Cavs gave the ball away 15 times and the Celtics capitalized for 15 points. Coach Tyronn Lue had been emphasizing it for two days, yet many of the Cavs' miscues were of the unforced variety.

A perfect example of Lue's greatest fear against the younger, faster Celtics came with 2:58 left in the third quarter when Love made a wild pass that rookie Jayson Tatum converted into a fast-break layup for a 74-58 lead.

Celtics coach Brad Stevens made the lineup switch most thought would come earlier in the series, inserting Aron Baynes alongside Al Horford and moving Marcus Morris to the bench. In the first four minutes, Love took advantage, scoring eight points.

But Baynes, 6-foot-10 and 265 pounds, provided added muscle inside as Celtics veteran Al Horford was held relatively in check by Tristan Thompson. Baynes brought a fiery attitude, along with added power on the boards, and the Celtics claimed a 45-39 edge on the glass. The Cavs held a plus-12 rebounding edge in the first four games.

The Cavs also struggled at the free-throw line, making 12-of-19 and were outscored 18-2 in fast-break points and 15-5 in second-chance points.

James led the Cavs with 26 points, 10 rebounds and five assists before exiting with 3:11 remaining, but made 1-of-6 from 3-point range and lost six turnovers. Love contributed 14 points and seven rebounds.

Three of the Cavs starters _ J.R. Smith (2 points), Thompson (1) and George Hill (7) _ combined for just 10 points as the Cavs hit their playoff-low in scoring.

Korver, who has become the Cavs' third scoring option in the postseason even though he is now coming off the bench, played only 18 minutes and made 2-of-6 field goals, including 2-of-5 from long range.

The Celtics had five players in double figures, led by Tatum with 24 points, seven rebounds and four assists. Jaylen Brown added 17 points. Horford contributed 15 points and 12 rebounds, and Baynes added six points and seven rebounds.

Tempers flared with 10:47 left in the second quarter when Shaker Heights High School product Terry Rozier shoved Nance, from Revere High School, from behind. When Nance got up, he scuffled with the Celtics' Marcus Morris. After a long replay delay, technical fouls were called on Nance, Rozier and Morris, an unpopular decision with the boisterous crowd. Korver made the resulting free throw and a 3-pointer off a Nance assist.

That started a 9-0 Cavs run that helped them cut the Celtics' lead to 36-28. Nance added a rebound basket and after Nance forced a jump ball with Brown, Jordan Clarkson hit a 3-pointer.

Clarkson, who played only four first-half minutes in Game 4, hit consecutive 3s as the Cavs cut a 17-point deficit to eight. But the Cavs got no closer the rest of the night.

The Celtics pushed it back to 14 with 2:25 left before halftime as Marcus Smart and Morris went to work. The Celtics led 53-42 at the half as the Cavs committed just one turnover in the second period.

That might not have seemed so formidable considering the two teams' playoff history. In the last 15 postseasons, the Cavs had two victories over the Celtics when trailing by double-digits at halftime, and the rest of the league had one, according to ESPN Stats & Info.

The Celtics also used their Game 1 stopper, Morris, on James. According to ESPN Stats & Info, Morris guarded James on 15 first-half possessions and the Cavs went 1-for-12 with two turnovers on those trips, with James going 0-for-1.

After Love helped the Cavs build a 12-9 lead, the rest of the first quarter was all downhill as the Cavs trailed 32-19 after 12 minutes.

The Cavs committed five turnovers in the quarter, which led to six Celtics points.

After making just 4 of their first 10 field goals, including 1-of-5 from long range, the Celtics got hot, canning 6 of their final 13 shots and 5 of their last 8 3s.

It wasn't the Cavs' worst quarter of the postseason (12 the third at Indiana on April 20), but it still felt that way. No Cav seemed in sync save for Love, and he picked up his second foul at the 47.6 second mark.