Henrik Stenson edges Phil Mickelson on day three at Troon

Golf - British Open

The 145th Open Championship has become a private party. The duel in the drizzle, 39 years on from epic events down the coast at Turnberry.

Phil Mickelson and Henrik Stenson apparently have little intention of allowing anyone else to gatecrash their scene. For golfers with scores so close, their target could hardly be more contrasting: Mickelson seeking a sixth major title as Stenson chases a first.

Mickelson, amazingly, has not won anything at all since lifting the Claret Jug at Muirfield in 2013. Suggestions that his list of achievements render him the favourite with 18 holes to play are offset by the occasionally outrageous pieces of good fortune from which he has benefited during the previous 54.

The American and Stenson spent Saturday slugging away at each other. It was enthralling if not electrifying, the noticeable lack of a boisterous atmosphere at Royal Troon testimony to that. Maybe cold, damp weather doused spectator emotion.

By close of play, Stenson led by one at 12 under par. The fine margins of the Open mean this is not exactly his tournament to lose. That said, he may have cleared a significant psychological hurdle on Saturday. “I know what I would like to see tomorrow,” Stenson said.

“There’s no question about it. But I’ve got a second and two thirds at the Open, so it’s not like I’m looking to pick up anymore of those finishes. There’s only one thing that matters tomorrow. I know he’s not going to back down, and I’m certainly going to try to not back down either. So it should be an exciting afternoon.”

After Mickelson, the next name on the board, Bill Haas, is minus six. A player other than Mickelson or Stenson could of course still walk off with the Claret Jug, but it would require either a spectacular collapse from them both or an inspired charge from behind. The likelihood of gusting winds on Sunday afternoon diminishes prospects of the latter.

Mickelson, 46, started round three at 10 under, one clear of his Swedish playing partner. The advantage was nullified on the opening hole, with Stenson two‑putting for birdie at the 5th to take this Open’s lead for the first time.

Mickelson, so typical with some wayward tee shots but magical recovery work, was again in front by the turn.

A ridiculous par save at the 12th, followed by a converted birdie attempt a hole later, meant the American, at minus 12, was two ahead.

Stenson again fought back on 14, where a two‑shot swing returned the previous scenario of joint leaders. Mickelson’s birdie at the par‑five 16th, where Stenson found a greenside bunker, placed him one up again.

We weren’t done. Stenson produced a wonderful birdie two at the 17th as Mickelson failed to get up and down from short left of the green. Pars at the last were something of an anticlimax, a Mickelson fairway rant at a photographer aside. The key statistic is this: Stenson’s 68 compared favourably with Mickelson’s 70.

“I was off today,” Mickelson said. “I didn’t have my best stuff. My rhythm was a little quick from the top as we started downwind. I was a little bit jumpy and my rhythm wasn’t very good. Today could have been a day that got away from me; instead, I shot under par and kept myself right in heading into tomorrow’s final round – so I’m proud of that.”

Sunday could well play out in matchplay fashion. The fact the protagonists are from either side of the Atlantic adds to the sense of a Ryder Cup situation.

“I’m looking forward to the opportunity,” Stenson said. “I’ve worked hard these first three days to put myself in this situation and I’m going to try my hardest to finish the job.” Still, it would be unfair to divert our entire attention towards just two competitors.

Haas has played every Open since 2010, claiming a hitherto best finishing position of tied 19th. His third round of 69 suggested he is coming to terms with this links business.

The adopted home hero is an Englishman. Andrew Johnston is five under par and closing in on his finest achievement since winning the Spanish Open earlier this year. Even if the amiable 27-year-old stumbles on Sunday, he has afforded himself a considerable following.

Bearded or chubby golfers tend to raise smiles. Not only does Johnston have both of those characteristics, he can play a bit. JB Holmes is a shot adrift of Johnston.

Rory McIlroy’s frustrations boiled over to the extent that he snapped his own three wood in a fit of pique on the 16th. The Northern Irishman’s 73 pushed him back to even par. Jason Day is a shot worse off following a Saturday 71, which included a shank on the 13th.

“I haven’t had a birdie on the back nine this week,” Day said. “I don’t know how many over par I’ve played it in, but it’s been terrible. That’s why I’m not in the tournament right now.”

Neither is Colin Montgomerie, but the Scot will be allowed some Open symmetry. At the course he calls home, Montgomerie was handed what he termed the “honour” of hitting the opening tee shot on Thursday. Now, 12 over par, he will again lead the field – alone, at 7.40am – on day four. Montgomerie will take this in his standard, congenial spirit. Won’t he?

guardian.co.uk © Guardian News and Media Limited 2010