That is according to four-time NBA champion and TNT ‘Inside the NBA’ analyst Charles Barkley.
The Celtics sealed their spot in the Eastern finals, which start on Sunday (1.30am), with a 114-112 win over the Philadelphia 76ers to complete a 4-1 series victory.
And they will face the Cleveland Cavaliers, led by James who has carried the team past the Indiana Pacers and then dominated the Toronto Raptors.
In last years Eastern finals, James averaged over 29 points as the Cavs beat the Celtics 4-1 in the series.
Marcus Smart and Marcus Morris will be key for the Boston Celtics
Charles Barkley has tipped the Cavs to beat the Celtics
Marcus Smart and Marcus Morris are the only two guys who can muscle LeBron James and try to wear him down
And with his weary legs given a short rest, James is likely to be at full power as he bids to reach an eighth consecutive NBA finals.
When asked who should guard James, Barkley said: “It’s got to be [Marcus] Morris and [Marcus] Smart. Nobody is going to stop LeBron.
“[But] they are the only two guys who can muscle him and try to wear him down.
“Tatum, Brown, Rozier and Horford are tough match-ups for anybody.
“I’m going to pick the Cavs but the Celtics have got four guys who are playing with so much confidence right now.”