His putting stroke is back, thanks to a tip from Steve Stricker at Doral, his irons are consistent and the swing changes he made in switching from instructors Hank Haney to Sean Foley appear to be complete.
Watson reached his 15th Test half century from 95 deliveries in the 30th over but once again the barrel-chested opener fell short of a three-figure score when he misjudged a reverse-swinging delivery, offering no stroke to a ball which moved back into his pads.
Australian Peter Fowler, who celebrates his 49th birthday on Monday, is a further strokeback after a 67, sharing third place with New Zealander Mark Brown.
On the stroke of half-time Davis had the chance to extend the lead once again, but his penalty bounced back off the uprights and the half ended with Exeter leading 10-9.