Pádraig Harrington made a strong start to his Portugal Masters campaign at Vilamoura with an opening round of 67, but things could have been so much better.

The Dubliner raced into a strong position after starting from the 10th and making birdies on his first three holes.

And then, at the par four 15th, he holed out from the fairway for an eagle two to go to five under after five and stir up some thoughts of a possible 59.

Another birdie followed at the 17th – his eighth – and that possibility was becoming even more distinct.

However it was not to be as bogeys at the 18th and two holes later at the second put paid to that.

The three-time major champion couldn't rekindle the form of his front nine on the way in and made just one more birdie – at the fourth – to finish with around of 67, a total of five under and a share of 12th place, three shots behind leader Marc Warren.

Harrington is planning to return to the PGA Tour after this week as he hopes to secure a place in next April’s US Masters at Augusta.

However, speaking to Sky Sports after his round, the Dubliner said that he will play the final series on the European Tour if he wins this week.

Paul Dunne – who comes into this week almost assured of his playing privileges for next season but still with some work to do – struggled to a round of 73 which leaves him needing something special on Friday to make the cut.

The Greystone gofer is currently 102nd in the Race to Dubai standings with the top 110 come Sunday evening set to keep their cards for next year.

Even if he misses the cut there should be enough players between Dunne and the dreaded 112 spot (the top 111 will keep their card due to the fact that David Lingmerth is an affiliate member and his place does not count) for the 23-year-old to squeeze through.

However it looks to be all over for Michael Hoey who is well behind the top 112 and also looks set to miss the cut after matching Dunne with a 73.

Meanwhile Scotland’s Warren shot an eight under par 63 to top the leaderboard following the opening day.

The 35-year-old began with six successive birdies at Victoria Clube de Golfe before adding a further three after blemishing his card slightly with a bogey on the seventh.

Fellow Briton Eddie Pepperell also made a strong start to the competition on Thursday as he seeks to secure his Tour card for next season.

The 25-year-old, who needs to retain his current ranking to make the cut, sits one shot off the overnight lead in joint-second position with Finn Mikko Korhonen, America's David Lipsky and the British pair of Matthew Baldwin and Callum Shinkwin.

Baldwin, 30, needs a top-two finish this week to keep his card and he hit eight birdies in the opening round, although a bogey on the seventh blotted his copybook.

Chris Paisley is among a group of five players a shot further back on six under, along with Swede Jens Fahrbring, who also needs a top-two finish, and Spaniards Alejandro Canizares and Nacho Elvira.

Defending champion Andy Sullivan, who last year secured victory by a tournament-record nine shots, is four strokes off the pace on four under.

He praised his supporters — dubbed ‘Sulli’s Army’ — for helping him through a bogey-free opening round.

“Front nine, I felt a little bit down the way I was playing and not really converting and they (the supporters) kept me going for a long time there,” he told europeantour.com.

“Then the back nine I started to play better and give myself more chances.

“It’s down to them that I probably played that little bit better today. If I didn’t have them there, I could have fell into the doldrums after that front nine. Thank ‘Sulli’s Army’ for getting me through that.”