SYDNEY, Dec 6, 2012 (AFP) - Senden, fresh from his finest season on the US PGA Tour where he had five top-10 finishes, collected eight birdies in his round.
The 41-year-old, an Australian Open winner six years ago at Royal Sydney, led the field from Rose and four others -- New Zealand's Gareth Paddison and Australians Brendan Jones, Kim Felton and Richard Green -- who were all on four-under 68.
"I am playing some of the best golf of my life. I need to believe in that and keep going forward," Senden said.
Teeing off early, Senden took advantage of the perfect scoring conditions to make the turn at five-under. And despite two bogeys in the middle of his round he recovered to finish with two birdies.
"We had perfect conditions this morning, teeing off at seven o'clock. You won't get much of a better day," he said.
Rose also made a hot start, picking up three birdies in the first four holes on the way to a front-nine 32.
The world No.4 dropped his only shot of the day when he fluffed a greenside flop shot on the par-4 third.
"I decided to try and hit the high, sexy lob - that didn't really come off," Rose said.
Using his broomstick putter after experimenting with a shorter blade in the lead-up, pre-tournament favourite Adam Scott squeezed out a par 72, while defending champion Greg Chalmers hit a one-under 71.
Among the casualties from the afternoon starters were eight-times major champion Tom Watson, who carded a six-over 78.
Contesting the Open for the first time since 1985, Watson dropped six shots in four holes amid a horror stretch on the front nine.
"I'm embarrassed," the American great grimaced.
Teenage Chinese sensation Guan Tianling is also in grave danger of missing the halfway cut following his nightmare 10-over 82.
The best of the Asian contingent was Indonesia's Rory Hie, who was in a tie for 43rd place on one-over 73 after an opening round of two birdies and three bogeys.
Five Australian golfers made a frantic dash from Japan to arrive just in time for their afternoon rounds.
Mike Hendry, Ryan Haller, Adam Bland, Aaron Townsend and Paul Spargo arrived at The Lakes with only minutes to spare before a round they feared they may not get to play at one stage.
The quintet had been competing at the the Japan Golf Tour Qualifying School and knowing they had to stay for a seminar on Wednesday they were always going to be cutting it fine.
Spargo was the best performer of the late arrivals, carding an impressive two-under 70 ahead of Hendry (72), Bland (75), Townsend (75) and Haller (76).
Scores after the first round of the OneAsia co-sanctioned Australian Open at the par-72 The Lakes course on Thursday (Australia unless stated):
66 - John Senden
68 - Kim Felton, Justin Rose (ENG), Gareth Paddison (NZL), Richard Green, Brendan Jones
69 - Stephen Allan, Nick Flanagan, Marcus Fraser
70 - Peter O'Malley, Stuart Appleby, Nick Cullen, Mahal Pearce (NZL), Marc Leishman, Josh Geary (NZL), Paul Spargo, Timothy Wood
71 - Mathew Goggin, Nick O'Hern, Peter Lonard, Jason Scrivener, Andrew Kelly, Kieran Pratt, Greg Chalmers, Kurt Barnes, Daniel Popovic, Matthew Jones
72 - Terry Pilkadaris, Aron Price, Adam Scott, Kyle Stanley (USA), Leigh McKechnie, Daniel Nisbet, Cameron Smith, Cameron Percy, Damon Welsford, Matthew Ballard, Andre Stolz, Daniel Fox, Jamie Arnold, James McLean, Michael Hendry (NZL)
Selected scores
73 - Liang Wenchong (CHN), Tanutchan Puaktes (THA), Rory Hie (INA), Supravee Phatam (THA), Zhang Xinjun (CHN)
74 - Hu Mu (CHN), Geoff Ogilvy, Choo Tze Huang (SIN), Zhou Guowu (CHN), Zheng Ouyang (CHN)
75 - Garrett Sapp (USA), Choi Joon-Woo (KOR)
76 - Andy Zhang (CHN), Han Ren (CHN)
77 - Kim Do-Hoon (KOR), Pravee Visalkt (THA), Choi Seong-Jin (KOR)
78 - Liu Yuxiang (CHN), Tom Watson (USA), He Zeyu (CHN), Marcel Schneider (GER)
79 - Yi Cao (CHN)
80 - Da Quan (CHN), Ou Zhijun (CHN), Park Hyo-Won (KOR)
81 - Jason Kang (USA), Son Joon-Eob (KOR), Park Min-Jun (KOR)
82 - Guan Tianlang (CHN)
83 - Chen Jian (CHN)
84 - Jin Daxing (CHN), Park Sung-Hyuk (KOR)
91 - Li Xinyang (CHN)