Washington Diplomat Coach Gordon Bradley, recuperating from a 3 1/2-hour operation on his left hand, which was mangled in a lawn mower Monday night, said yesterday the next "48 hours will determine if I will lose the use of my thumb."

"They did a pretty good job of fixing my hand up," Bradley said from his hospital bed in George Washington University Hospital. "Right now, though, the thumb is a problem. The finger and thumb were pretty mangled up and I won't know how much mobility I'll have for awhile."

Bradley was working in his yard in Burke, Va., when the accident occurred. The drive chain came off on his power mower and Bradley tried to use a stick to put the chain back without cutting off the motor.

"The stick slipped and my hand got caught in the blades," said Bradley. "The mower has always been faulty. And I was trying to rush and get through. My hand was a mess."

Dr. Robert Neviaser, who performed the surgery, said the injuries included several bone fractures in the hand, torn tendons and muscles and nerve damage throughout the hand. The surgery also including sewing back the thumb and middle finger which had been partly severed from the hand.

Bradley will remain in the hospital for several more days and will miss the Washington-Dallas game at RFK Stadium Sunday. The team will be handled by Bradley's assistant, Joe Mallett.