German leads by four heading into the final round in Michigan
Bernhard Langer carded a six-under-par 64 to surge into a four-shot lead entering the final round of the US Senior Open in Michigan.
The two-time Masters champion opened with three straight birdies and eight in 12 holes saw him move five clear of the chasing pack.
A double-bogey at the short 13th halted the momentum, but he got the shot back at the 15th before making his only bogey of the day at the final hole.
The German has a group of five players chasing him on six-under par and he knows he will need to remain focused on Sunday.
"That's not a huge lead," said the former Ryder Cup winning captain. "That can disappear in no time. I'm going to have to get out there and shoot under par.
"If I go -2 or -3 it will be very difficult for anyone to catch me. And if they do, they deserve to win."
Major winners Corey Pavin and Tom Lehman had rounds of 68 - as did England's Roger Chapman and John Huston - to be part of the group four behind Langer, which is completed by Tom Pernice Jr.
Fred Couples shot 65 to lie a stroke further back while overnight leader and part-time player Lance Ten Broeck had a disappointing 72 that saw him close with two bogeys and a three-under-par total.
Playing partner Tom Kite shot 74 to slip back into the pack.
