Six-time major winner Trevino said the world number one must change the way he “locks” his left knee when attacking the ball or swing the club slower.
“The upside is if he changes it a little bit, if he learns to swing a little bit with the knee breaking, he won’t be able to swing as fast,” Trevino said in a telephone interview from his Dallas home on Friday.
“If he does that then he’s going to hit the driver straighter and if he hits the driver straighter he’ll be a better player than he is and they (the rest) are in bigger trouble.
“If he doesn’t stop that and he keeps locking his left knee and swinging at the same speed he’ll blow it out again. If he’s going to go ahead and lock the knee up, he’s going to have to slow his swing down.”
Woods, 33, who has been sidelined since undergoing surgery following his US Open win in June, is expected to return in time for the US Masters in April.
“I know he’s practising full time right now,” added Trevino. “Whether he’s trying to change his knee action I don’t know but I’m afraid for him.”
The 69-year-old said Woods could continue to dominate golf by slowing down his swing.
“Tiger learned how to swing differently than most of us,” said Trevino. “We learned to swing with some kind of flexing of the knees at impact.
“We always wondered how Ian Woosnam at 5’ 5” (1.65m) could hit the ball longer than anyone on tour and could never figure out why. He didn’t look like he was swinging any harder but he always hit the ball a long way.
“Then when Tiger came along and we saw Tiger swing at a golf ball, we understood. Tiger figured out that when you lock the left knee it makes his right hip and right shoulder travel faster, much faster ... and that’s what Ian Woosnam did.”
Trevino, however, explained the diminutive Briton swung a lot slower than Woods.
“The reason Woosnam never blew his knee out is he swung at about 110-mph (177-kph),” said the Mexican-American. “The left knee is your brake. Fortunately or unfortunately, Tiger swings at 130, 134-mph.”
Trevino described Woods as one of the finest competitors he had seen.
“He gets his confidence from hard work,” he said. “If he is hurt he is not going to be able to work and if he is not working on his game, he will quit,” he said.