Colin Montgomerie believes Peter Hanson has it all to prove as he chases his maiden major title in the final round at Augusta.
The Swede leads by a shot after a sensational seven-under 65 on Saturday. However Mickelson - a three-time Masters champion - is just one shot behind Hanson after four birdies on the back nine put him firmly in contention for the Green Jacket.
Hanson and Mickelson will be the final pairing on Sunday and Montgomerie believes the former champions' experience and support around Augusta could give him a vital edge in the final round.
Hanson has only made one previous appearance at the Masters and Mongomerie fears the 34-year-old could feel the pressure of leading the tournament.
"We have not seen Peter Hanson go into a Major in a lead to see what he can do," Montgomerie told Sky Sports. "The proof of the pudding will come tomorrow playing with Phil Mickelson
"I have been the there with Tiger and been there with Phil in these events and it is not easy. It is not easy. If Phil gets off to a decent start Peter Hanson has got a long day ahead of him.
"But if he can handle playing with Phil Mickelson and stay one ahead all credit to him."