Ireland's Des Smyth, runner-up at Royal Aberdeen last year, is one shot off the Senior British Open leaderboard at Turnberry but American players dominated the opening round.
Peter Jacobsen posted an early target for the rest of the field when he overcame a painful hip problem to card a 65.
But Jacobsen had to settle for a share of the lead when Craig Stadler and Loren Roberts matched their countryman's effort late in the day.
Jacobsen said: "I have been struggling with a bad hip which is going to need some medical attention this winter and I wasn't sure I was even coming.
"But because of this venue and the fact I love playing in the Open, I did everything I could to come.
"I had a couple of procedures last Thursday. I had an epidural to reduce some pain in my back and also some platelet gel injected into my left hip.
"My doctor told me to wait until Sunday morning to hit balls to see how I felt. So I went out and hit some balls and jumped on a plane at two o'clock on Sunday afternoon."
Stadler, who managed to find just six fairways, bagged an eagle there at the 17th to serve notice of his intent.
Tim Simpson ended the day one shot adrift of the leaders, confirming he has fully recovered form the brain surgery he underwent 17 months ago to alleviate the effects of a tremor in his hands.
Simpson's score was equalled by Smyth.
Evergreen Gary Player shot 69 to beat his age by a year and claimed: "Of all the times I have done that this gives me the most satisfaction because Turnberry is among my top 20 favourite courses."
Tom Watson, winner at Turnberry in 2003 and Royal Aberdeen 12 months ago, made a faltering start to his defence when he carded a round of 73.
Watson said: "It wasn't a good day but 73 is not all the way out of it.
"This golf course is playing a little tougher than three years ago with all those bunkers in the way and I got what I deserved."
While Smyth leads the nine-strong Irish challenge, Mark McNulty is also faring well sitting as he does on two under. Denis O'Sullivan is level par while Eamonn Darcy is one shot further back.