Many of us can probably empathise with Phil Mickelson. “It’s just gotten more difficult as I’ve got older to focus for longer periods of time,” said the 50-year-old. We hear you Phil. This correspondent’s mind, for instance, was beginning to wander halfway through typing that opening sentence.

Nothing focuses the golfing thoughts like a major championship, though. And Mickelson certainly got himself tuned into the task in hand during the second round of the US PGA Championship at Kiawah Island yesterday.

Rolling back the years, turning back the clock? Call it what you like. Mickelson was doing it during an absorbing three-under 69 which hoisted the five-time major winner into the early clubhouse lead with a five-under aggregate. He remained there for the rest of the day and was eventually joined at the top by Louis Oosthuizen, who was leading on his own until he spiled a shot on the 18th in a 68.

The leading duo finished a shot ahead of two-time US PGA champion Brooks Koepka, who made two eagles during a menacing advance but stumbled with a couple of late bogeys.

On a devilish Ocean Course which certainly teases and torments the mind, Mickelson displayed great mental fortitude and plenty of graft and craft as he stayed in the hunt to become the oldest major winner. That record was set in the US PGA championship of 1968 by Julius Boros, who was 48. Golf remains a wonderful generation game.

During Thursday’s first round, Mickelson had bogeyed four of his first six holes but rallied to post a 71. Yesterday, the 2005 US PGA champion was three-over at the turn but came bounding home like an auld dog showing it had plenty of life left in it.

A rousing haul of five birdies on his back-nine, which was concluded with a 22-footer on the last, was very much in the Phil the Thrill mould. It wasn’t the here, there and everywhere performance that we used to expect of Mickelson, however. He hit 11 of 14 fairways with a controlled, composed display of savvy and stoicism.

For all of the Ocean Course’s vast expanse – it does have the potential to play as the longest in major history – it’s that wee bit between the ears that has been key to Mickelson’s success so far this week.

"I'm working on it,'' said Mickelson of getting his head screwed on for this mind-mangling test. "I'm just making more and more progress just by trying to elongate my focus. I might try to play 36, 45 holes in a day and try to focus on each shot so that when I go out and play 18, it doesn't feel like it's that much. I'm trying to use my mind like a muscle and just expand it, because as I've gotten older, it's been more difficult for me to maintain a sharp focus, a good visualization and see the shot.

"Physically, I feel like I'm able to perform and hit the shots that I've hit throughout my career but I've got to have that clear picture and focus. So these first two days have been much better.''

Now languishing down in 115th spot on the world rankings, perhaps Mickelson, for years the game’s eminent left-hander, has been spurred on too by Robert MacIntyre’s emergence as golf’s leading lefty on the global order?

Mickelson, a two-time winner on the over-50s tour last year, was remaining coy about his chances of winning again on the main circuit “Right now there’s a lot of work to do,” he said. “But the fact is I’m heading into the weekend with an opportunity." 

His playing partner Padraig Harrington, the 49-year-old  European Ryder Cup captain who is making admirable progress at level-par, was more bullish about Mickelson’s major ambitions.

"I think he believes he can do it in these conditions, just like myself,'' said Harrington, the three-time major winner who captured the US PGA crown in 2008. "I think like myself, Phil would find it easier to compete on this style of golf course in these conditions in a major tournament all the time. I think he has the bit between his teeth."

In the to-ings and fro-ings among the early starters, South Africa’s Branden Grace had set a sprightly pace but having covered 16 holes in four-under, he leaked three shots on his closing two holes in a 71 to finish two strokes behind Mickelson.

Just 18 players are under par following the second round  but 24 are within five shots of the joint leaders. Glasgow’s Martin Laird cemented his place in the upper reaches with a battling 73 which left the four-time PGA Tour winner on one-under and in a share of 12th.

Rory McIlroy, the runaway champion at Kiawah Island in 2012, mounted a second day assault after his opening 75 but a trio of late bogeys in a 72 left him on three-over. MacIntyre, meanwhile, is a stroke further back after a 73. It’s now five cuts made in five major appearances for the young Oban left-hander. It’s the auld lefty Mickelson, though, who is the man to catch.