Calcavecchia, the 1995 winner, continued his solid play with an eagle at the par-four fifth hole, added five birdies to his seven-under effort, and was one shot in front of unheralded Steve Flesch and Mexico's Esteban Toledo.
Six more players, including PGA Tour money leader David Duval, were two strokes back, three of them in the clubhouse and three more on the course. Duval, coming off his second victory of the year at last week's Houston Open, is one of three players in the clubhouse on 67, along with Scott Verplank and Glen Hnatiuk.
Tiger Woods - like Calcavecchia making his first appearance since the Masters - carded a three-under 69 to lie four shots off the lead.
Britain's Tommy Horton fought off a severe stomach upset to return an opening round of 70 in the Beko Seniors Classic at the Gloria Resort course in Turkey yesterday. This left the defending champion two strokes behind the tournament leader, Geoff Parslow of Australia.
Horton was hit by a bout of gastroenteritis early last month before going to play in America but thought it had cleared up. It returned on Thursday afternoon, though, and he said: "It makes me feel sick, tired and listless and at the moment I'm frightened of eating or drinking anything."
But Horton, who won in Spain last weekend, was delighted with his round and quipped: "It's nice to have a new face at the top of the leader board for a change."Reuse content