Those three hold a four-stroke lead on Dave Stockton, Jim Thorpe, Ed Dougherty, Tom Jenkins and Gil Morgan. Those five golfers are at 7-under- par 209 through three rounds.
Despite the three-way tie for the lead, one should not expect a playoff tomorrow. There have only been two playoffs in the previous 20 Senior Players Championships.
Stadler, a Champions Tour rookie, got going quickly at the TPC of Michigan. He rolled in his first birdie at the par-4 second. He sank another birdie try at the next, then made it three straight with a birdie at the fourth.
The Walrus settled down a bit from there. He rolled off three consecutive pars. He moved to 8-under with a birdie at the par-3 eighth.
Around the turn, Stadler drained a birdie putt at the 10th. He climbed into double-digits under par with a birdie at the par-5 13th. He capped his round with a birdie at the par-5 17th.
'I putted very good today, which is kind of what you're looking for,' said Stadler, who needed just 24 putts in the third round. 'I haven't done it in ages. It's nice to get over a putt and feel like you've got more than a one- percent chance of knocking it in.'
Watson struggled to get going and saw his two-stroke advantage slide away. He was able to move to minus-11 with a birdie at the par-4 fifth.
On the back side, Watson climbed to 12-under with a birdie at the par-3 12th. He stumbled to his first bogey in 37 holes, when he could not save par at the par-5 17th.
'It was the first round that I drove the ball just out of play, either in the shortcut or the rough,' said Watson. 'I just didn't get the ball in the fairway enough times to be aggressive. I had to play defensive golf most of the day. I did make three good pars putts though.'
Watson stressed he is still trying to get a win for his long-time caddie, Bruce Edwards, who is fighting ALS or Lou Gehrig's disease.
'One of my goals is to win again with Bruce on my bag and cherish that hug on the 18th hole,' Watson said. 'I hope tomorrow is the day. I'm going to have to shoot in the 60s to win this golf tournament tomorrow.'
McCullough used a strong front nine to grab a share of the lead. He got going with a birdie at the par-5 third. He followed that with a birdie at the sixth and made it two in a row when he sank a birdie putt at the next. Around the turn, McCullough managed just one birdie at the par-4 16th on his way to a 4-under 68.
'Fortunately I made putts when I had to and salvaged some otherwise disastrous holes,' McCullough said. 'I'm aiming at my targets and missing then pretty badly, but I am missing them in places I can still play.'
Dana Quigley is alone in ninth after shooting a 4-under 68 to move to 6-under-par 210. Tom Kite is one stroke further back at minus-5. Terry Mauney and television commentator Andy North share 11th place at 4-under-par 212.
Defending champion Stewart Ginn struggled to a 1-over 73. He stands at even- par 216 and is tied for 20th.