Padraig Harrington will slam the accelerator to the floor and put his engine under maximum pressure when chases down Phil Mickelson and Scott Verplank in the final round of the Shell Houston Open tonight.

With the Masters just around the corner, the Dubliner knows that he needs to cast off the shackles and let rip at Redstone, where he did well to finish with no worse than three successive bogeys in a third round 70 to slip four shots off the pace.

It was a disappointing end to what looked like being a promising day for the three-time major winner, who has only recently taken the training wheels off his new-look swing and pre-shot routines.

He needs to have total confidence in his game to stand up and go for his shots without fear for the consequences, especially at Augusta National. And while he blew up over the last three holes on Saturday, he knows he needs to be even more aggressive today with the top-15 players covered by no more than five strokes.

If he is to win for the first time in the US since his US PGA victory in 2008, he will need help from the leaders and the weather.

But he likes his chances.

“It’s a very tricky golf course to lead on,” said Harrington after holing a six and a half footer to save bogey at the 18th. “You’re cutting across all the doglegs, and there’s a hazard inside and outside of all the doglegs.”

He also knows that he will have to make birdies and while the leaders will be trying to hold on to what they have, he’s prepared to go on the attack.

“You will always see good scoring on this golf course from guys who are freed up and chasing, and you’ll always see the leaders finding a lot of trouble,” Harrington said.

“If it’s a windy day tomorrow, that would put a lot of pressure on guys trying to hold on to their score and, as I said, I don’t have anything to lose, so I should hopefully have a little more freedom than I showed today.”

Left-hander Mickelson burst into life after some recent struggles with a course record equalling, bogey free 63 that came just in the nick of time with his Masters defence around the corner.

But Harrington is also looking good, albeit with some reservations about his ability to fully trust himself.

He picked up three early birdies in Saturday’s third round and was right there in the thick of the action coming down the stretch after mixing a solitary bogey at the 10th with birdies at the eighth, 12th and par-five 15th.

But as he slammed the accelerator to the floor in what amounts to a trial run for next week’s Masters, Harrington he bogeyed his last three holes in disconcerting fashion.

At the par-three 16th, he missed the green way to the right and did well to get up and down for a bogey four. At the 17th, another tough hole, he was way left off the tee and failed to get up and down from greeside sand, missing a nine footer for his par.

The finishing hole is defended by a large lake on the left hand side and bunkers on the right. But while Harrington found the water off the tee, it is a sign that he at least took on the tee shot.

He also saved a brave bogey when he two putted from 20 yards by making a testing six and a half footer.

But he will need to produce a round in the 60s to have any chance today and there are some big names ahead of him, including Mickelson.

The Masters champion was at his brilliant best in a nine-birdie day, especially at the sixth, where he drove into the hazard, over shot the green with his third and then chipped in for par.

Billy Foster, caddie to playing partner Lee Westwood, got down on his knees to pay homage to the master after that one.

While Westwood shot a 74 to slip back to 57th on two under, they both know that this is only shadow boxing before the leather really starts flying next Thursday.

Mickelson picked a great time to shoot a great round and revealed that he may use two drivers at Augusta once more.

Asked if his round gave him confidence heading to Augusta, he said: “It doesn’t hurt. I mean I knew that I was close gamewise but I hadn’t been putting together the score. To get a good round like this means a lot.

“Also to have the challenge of tomorrow, you know, to be in contention, to be in the final group, have an opportunity to win, I really enjoy that opportunity, that challenge, and I think it’s good for me to be in that position heading into next week, too.”

Harrington would echo those words. After a series of false dawns on weekends over the past 12 months, it’s time he made a move in the right direction.