NORTON, Mass. — On a day when Phil Mickelson played his way into contention at TPC Boston, halfway co-leader Bubba Watson clung to a one-shot edge over five players heading into the Deutsche Bank Championship’s Labor Day finish.

Add the gang of 18 golfers closing to within four shots of the lead after Sunday’s third round and the second of four FedEx Cup playoff events will be anybody’s ball game. Recalling Charley Hoffman’s come-from-behind win from four shots back last year, tomorrow promised another exciting ending to the only PGA Tour tourney with a scheduled Monday conclusion.

Phil Mickelson relies on his ball-striking to move into contention for the Deutsche Bank Championship (Photo: Jim Rogash/Getty Image)

Despite his start and some wild play on the back nine, Watson was able to card a 1-under 70 for an 11-under for the tourney. The three-time PGA Tour winner began with a bogey but quickly added three birdies in six holes and made the turn with a 34.

After getting to 13-under through 10 and looking to put some distance between himself and the field, Watson struggled off the tee. Three bogeys in five holes on the back nine brought him back to the pack that included Adam Scott , Jason Day, and University of Harfford grad Jerry Kelly, each of whom ended the day one shot off the pace. Defending FedEx cup champion Jim Furyk, World No. 1 Luke Donald, and reigning Masters titleholder Charl Schwartzel each headed into Monday just two back..

“When I made the turn I made a good par on nine, birdied 10…so I knew if I could put the gas pedal down I could get a big lead,” Watson, appearing far more relaxed than he did after Saturday’s round, told Golf Channel’s Steve Sands. “But I just made some swings, gusty winds, second-guessing myself, and made two bogeys back to back there. Coming down the stretch I birdied 17 to get the lead by one, but it’s good position overall.”

And then there was Mickelson, who, with the day’s low round of 63 battled his way back to 7-under and put himself into the mix after barely making the cut on Saturday. Lefty’s flawless round included three straight birdies early on.

A blistering start to his back nine, with two consecutive birdies and an eagle at the par-4 12th from the rough some 173 yards out with a 7-iron, had Mickelson flirting with a 59.

“Oh, yeah, absolutely,” he said about whether he believed the low number was within reach. “Had I made a couple of putts thereafter, I might have had a chance.”

While he was unable to post the magic score, a final-hole two-putt birdie from 10 feet put an exclamation point on the round for Mickelson, who continued to wield a belly putter — for how long even Phil would not venture a guess.

“It didn’t go as well as I had hoped the first couple of days, but…it’s something that I need to spend a little more time on and I’ll probably do that in the off-season,” he said. “It comes off at a different speed. It’s a lot heavier, so it’s taking some adjustment from me on the breaking putts. But on the straight putts it’s great because it seems to start the ball on line very easily.”

Does that mean the big bat is in Phil’s bag for good? Not necessarily.

“There’s some things I really like about it, and there’s some things that are challenging, and I’ll probably spend some more time with it in the off-season,” Mickelson said. “I’m not sure what I’ll do at the start of the year next year, but my curiosity was very high, especially after not putting great last week. I may experiment some more with it tomorrow or [at the BMW Championship in] Chicago, I may not. I’m just not sure.”

Even with all the focus on his putting this week, it was the way he hit the ball that most impressed the golfer.

“It was a good ball-striking round….one of the best I’ve had,” said Mickelson, who noted the longest birdie putt he made was an eight-footer on 11. “Today I struck it as well as I have in a long time.”

Indeed, Mickelson, who spent a long while on the putting green after his first day with the long stick, said he had not practiced hitting much since starting his experiment with the new flat stick.

“After last week’s Barclays event I spent only time on putting and trying to get that down for this week. I neglected my ball-striking a little bit and consequently I didn’t hit it very well the first two days,” said Mickelson. “But I talked to [coach] Butch [Harmon] last night and we kind of sorted it out. It was just a slight adjustment because I’ve been striking it well. I came out today and hit it really well.”

(Emily Kay is a regular contributor to New England Golf Monthly. Check her out on the Waggle Room, Boston Golf Examiner, National Golf Examiner, and GottaGoGolf websites. You may also follow Kay on Twitter @golfexaminer.)