The 44-year-old Furyk, the 2006 winner at Hamilton and 2007 champion at Angus Glen, matched Petrovic at 10-under 130 at Royal Montreal. Petrovic followed his opening 64 with a 66.
The 47-year-old Petrovic was the last player to get in the field, grabbing a spot when Benjamin Alvarado withdrew Tuesday. Petrovic won his lone
Graham DeLaet, trying to become the first Canadian winner in the event since 1954, matched Furyk's 63 and was two strokes back along with Kyle Stanley.
Bernhard Langer has a seven-stroke cushion to take into the third round of the Senior
The German is at 11-under 131 overall at a sunny Royal Porthcawl, with Scotland's Colin Montgomerie and South African-based Englishman Chris Williams tied for second.
Spaniard Pedro Linhart (69) was another shot back in fourth, while Americans Bob Tway (73) and Tom Watson (66) shared fifth at two under.
The United States shuffled its lineup in the second round of the