Defending champion Sergio Garcia, after opening with a pair of 69s, shot 77 and plummeted 52 spots on the leaderboard, to a tie for 62nd. All Garcia's damage came on the back nine. He made the turn in 1-under 35, then started the back with a birdie on the par-5 10th. He would make only one more birdie, to go along with three bogeys, a double bogey and a triple bogey.
Grace's 4-under round of 68 featured a remarkable birdie after driving into the trees on the fifth hole. He snap-hooked a wedge to 6 feet to stay in contention.
''I could only hit a big, snapping hook with a wedge and when I hit it, I couldn't see the ball,'' Grace said of his near-impossible shot.
''We heard the claps and next thing you know, managed to make a nice little 5-footer for birdie that definitely got it kick-started.''
Wiesberger also carded 4 under, while Grillo shot a bogey-free 5-under 67 to be in contention for his maiden European Tour title.
Grillo putted magnificently, including a 20-foot birdie on the 11th.
''I hit the ball better today, so I've got a good feeling for tomorrow, and want to try to get my first win,'' Grillo said. ''You have to learn first to win out here, and I've learned a lot.''
Wiesberger got off to a flying start when he birdied the second and third before converting another birdie from 15 feet at the eighth.
''It's nice to start the day in the lead and hang on to keep it,'' he said. ''It was just that bad swing on 16 which cost me a bogey there ... I finished nicely with a birdie and it gives me a bit of momentum for tomorrow.''
Warren made four birdies in his first 10 holes, but bogeyed the 14th before making birdies on the next two to match Grillo's score for the day.
''The last few years I've shown a lot of progress again,'' Warren said. ''It's one thing to be confident, and to actually do it is another thing. I've definitely got a spring in the step.''
Pepperell, who celebrated his 24th birthday on Thursday, carded Friday's best round of 7 under to be at 11 under with Canizares and Coetzee.