Pádraig Harrington's slim hopes of booking his Masters ticket with a win in the Arnold Palmer Invitational evaporated with a one over 73 at Bay Hill on Saturday.

As Graeme McDowell put a new driver in the bag and hit 10 fairways to card a 67 — 10 shots better than Friday — to move up to joint 19th on four under, Harrington fell back to 29th on three under after another frustrating day on the greens.

Adam Scott shot 71 to see his overnight lead reduced from seven shots to just three over Keegan Bradley on 15 under par.

Harrington ended the day 12 shots off the pace and while the three-time major winner had just 28 putts, that statistic does not tell the full story.

Despite hitting 11 greens in regulation, both his birdies came at par fives with one a chip-in at the third and the other courtesy of a 30 foot putt at the 12th after back-to-back bogeys at the eighth and ninth saw him turn in 37.

Five of his other six single putts were for par and a three-putt bogey from 22 feet at the last just about summed up his day.

As for McDowell, the Orlando resident was pleased to recover his driving prowess.

After hitting just four of 10 fairways with the his new Srixon driver on Friday, he changed club and found 11 out of 11 with it in round three and made five birdies in an immaculate round.

"Improved driving today was a combination of a different driver and some technical fixes," McDowell tweeted. "Was not maintaining loft on way back. #left"

Scott struggled early at Bay Hill, three-putting the first for bogey and dropping another shot at the fifth to see his seven-stroke overnight lead reduced to one stroke.

He birdied the sixth and turned in one over par but while he got as far as five ahead at one stage on the back nine, a homeward 34 featuring four birdies and two bogeys was not enough to build a huge cushion.

Bradley raced home in 31, starting and finishing the back nine with birdie hat-tricks, to card a 66 to join Scott in the final group just three adrift on 12 under.

Another four players are within five of Scott's lead — Matt Every (66) and Jason Kokrak (67) are four behind on 11 under with Chesson Hadley (69) and Francesco Molinari (69) only five behind.

Still, Scott was looking on the bright side as he eyed a win that would almost certainly mean he will arrive at Augusta National for his Masters defence as world No 1.

"It was a good fight back after a tough start, when I wasn't doing too much wrong, but I made the errors, myself," said Scott, who had to hole a seven footer to avoid a three-putt bogey at the last.

"This course is tough when you're on the back foot. I was pretty pleased with the way I played the back nine. I missed a couple of short par putts, which would have been nice to make. But I'll have to make them tomorrow, because that's how you win events."

He added: "I really enjoyed the day on the course. I think I'm feeling better physically. But I also enjoyed the challenge of playing in contention again for really the first time this year. 

"I'm looking forward to tomorrow. It's going to be a great day. Everyone will be hungry to try to win this event. I think it means a lot to every player out here."

He added: "I've got a bunch of guys breathing down my neck who all have had nice rounds today and feeling pretty good about the way they're playing going into tomorrow. So I'm going to have to play a pretty sharp round of golf and not open the door at all."

Bradley is happy with the way he is putting again thanks a heart-to-heart with Dr Bob Rotella.

"I'm excited that I cut into the lead," Bradley said. "My goal today was just to cut into that lead as much as I could. I kind of like being in this position going into Sunday. I needed to go shoot a good round. I feel really good.

"I'm playing really, really solid golf. I just need to go out and do my thing tomorrow and keep hitting a lot of fairways and a lot of greens. My putter seems to have woken up a little bit, which is a really good sign. I'm making a lot of 15‑, 20‑footers, which you have to do out here."