GOLF:ONCE UPON a time, Phil Mickelson's unpredictability was part of his charm. It even inspired a series of television ads from motor manufacturers Ford with the catch-line, "What will Phil do next . . .?"

Yesterday, as the WGC-Bridgestone Invitational reached its midway point at Firestone Country Club in Akron, Ohio, it seemed Mickelson and British Open champion Pádraig Harrington - the top-ranked players in the world competing here - had undergone some sort of body swap.

Mickelson played, for the best part, error-free golf that enabled him to take the halfway lead after adding a 66 to his opening 68 for a 36-hole total of 134, six under.

But Harrington, competing for the first time since reclaiming the Claret Jug in the British Open at Royal Birkdale a fortnight ago, seemed to take a leaf out of the old Phil's book and negotiated as adventurous a route as possible.

So it was that much of Harrington's afternoon - hot and humid, for good measure - was invariably spent playing shots from the rough, from bunkers and, on occasions, from behind trees.

It all amounted to a disappointing second round that featured no fewer than seven bogeys on the way to a 75 for 144, down towards the wrong end of the scoreboard.

"It wasn't a good day, but there's no point in being frustrated. I just won the Open in my last tournament, so I'd be silly (to get frustrated)," said Harrington.

"I struggled with my focus today and I struggled with my short game particularly . . . missed a few putts early on and everything seemed to slip away after that.

"I know I've another 36 holes to improve where I am. But it is a golf course where I've always struggled, with a few funny alignments off the tee.

"It is all about (preparing) for next week now. I need to get my chipping a little bit better out of the rough, getting myself into the mindset for next week. I'm happy to have another two rounds opportunity to do that, but I'm not going to overdo things. I'm suffering a little bit from fatigue."

In contrast, the new Mickelson was in control. Yesterday's round, admittedly, featured a bogey - on the eighth, his 17th - but that was his only bogey in 36 holes of golf, and the five birdies the world's number two produced enabled him to claim the clubhouse lead, a shot clear of a quartet that featured Peter Lonard, Sean O'Hair, Zach Johnson and Lee Westwood.

Out on the course, Vijay Singh moved to seven under through 14 holes of his second round to overtake Mickelson.

With no Tiger Woods to worry about, this week offers all sorts of opportunities for Mickelson. After all, he has never topped the US Tour money list in Woods's era and, currently third on that table (just over $1.7 million behind Woods, who is out injured for the rest of the season), a win here would put Mickelson within reach of that particular milestone as the season reaches a climax.

What's more, a win would also represent a piece of history for Mickelson: he has never won a WGC event.

If there are those who see this week as much about fine-tuning for next week's US PGA championship at Oakland Hills - and Harrington possibly falls into that category, especially coming so soon after his Birkdale triumph - Mickelson is the kind of player who likes to play well, even win, going into a major.

Indeed, his last major win, at the US Masters in 2006, came a week after he won the BellSouth in Atlanta.

"I prefer that. I feel like it is a better way to go (into a major), playing well," he remarked.

In the past, Mickelson's waywardness has manifested itself off the tee, most infamously on the 72nd hole of the US Open at Winged Foot in 2006 where he carved a drive into the trees in running up a double-bogey.

In more recent times, it is his once imperious short game that has let him down. However, he has spent a considerable amount of time on that aspect and it was evident yesterday as he played some wonderful lob shots, like of old, in saving pars whenever it looked as if the round might get away from him.

Nowhere was this invigorated short game more obvious than on the fourth, where he overshot the green but then played a wonderful lobwedge to 12 inches for a saving par.

"It's a lot better," Mickelson observed of his short game play here. "I feel much, much better with the putter, much better with the wedges. I haven't been performing the way I expected (recently) and this week it feels much better. I spent last week working exclusively on my short game and I feel like it is starting to come around."

Paul McGinley, after a 67 for 137, heads the Irish challenge, but Graeme McDowell - who started like a train, birdieing three of his first four holes - signed for a 71 for 141, while Darren Clarke also finished on that mark.

"I'd a few chances and didn't take them, but there is a score out there," insisted Clarke.

The leading European was Westwood, back on American soil for the first time since finishing third at the US Open in June.

The former European number one shot a sparkling five-under-par 65 for a five-under total of 135.