SAN FRANCISCO, June 3 — Al Horford led an electrifying comeback as the Boston Celtics stunned the Golden State Warriors 120-108 to draw first blood in their best-of-seven NBA Finals series on Thursday.

Celtics veteran Horford scored 26 points, including 11 in the fourth quarter, as Boston inflicted Golden State's first home defeat of the post-season at their Chase Centre fortress.

Horford's tally included what turned out to be a decisive burst of eight unanswered points in the fourth quarter as the Celtics pulled clear having trailed by 12 at the end of the third quarter.

Boston defensive linch pin Marcus Smart also came up big late on with back-to-back three pointers as the Celtics surged into a double digit lead against a shellshocked Warriors.

The victory was no less than Boston's gutsy never-say-die approach deserved.

Boston twice recovered from double-digit deficits either side of halftime when it looked as if the Warriors were poised to cut loose.

Not even a dazzling shooting display by the Warriors' Stephen Curry — who exploded for 21 points in the first quarter alone including a record six three-pointers — could fluster the Celtics.

Despite a vastly less experienced line up — not a single player on the Boston roster had played an NBA Finals game before Thursday — the Celtics refused to crack under pressure.

Instead it was the Warriors whose resistance crumbled in a fourth quarter that saw the home side outscored by an astonishing margin of 40-16.

The Warriors have the chance to level the series in game two in San Francisco on Sunday. — AFP