Jason Day, tied for the lead at the RBC Heritage entering the third round, struggled to the beat of an eight-over 79 at Harbour Town Golf Links in Hilton Head, S.C. on Saturday, nine shots behind leader Luke Donald.
"I'm a little tired physically and mentally, but that's just what it is," said Day. "Last week I felt like I had gone ten rounds of a championship fight. I was talking to Brandt Snedeker today about it, he finished T-10, as well, with me. It beat us up, it really did. Physically and mentally beat us up last week."
Donald, seeking his first PGA Tour victory since 2012, shot a two-under par 69 to ascend into sole possession of the lead. At seven-under, he leads Charley Hoffman and Jason Kokrak by a stroke. Hoffman held the lead after a birdie on 16, but bogeyed the final two holes.
Zach Johnson, winner of the 2015 Open Championship, shot a one-under 70 to move into a tie for fifth place with Branden Grace, Chris Kirk and Kevin Chappell. At four-under, they are three shots off the lead.
Matt Kuchar, the winner of the 2014 RBC Heritage, shot a one-over 73, moving down to a tie for ninth. He is four shots off the lead at three-under.
Bryson DeChambeau struggled in his third round since turning professional earlier in the week, shooting a one-over 72. He is tied for 14th at two-under.