Adelaide - Tasmanian Richie Porte blew the Tour Down Under field wide open on Willunga Hill on Saturday but just failed to overhaul Rohan Dennis as overall leader of the UCI season-opening race.
Just as he had in 2014, Porte launched a stunning attack on the second and final climb up the notorious Willunga Hill to win the 151.5km stage in 3hr 37min 32sec.
Dennis crossed the line nine seconds behind Porte to retain the leader's ochre jersey by two seconds heading into the final stage through the streets of Adelaide.
Spaniard Ruben Fernandez (Movistar) finished third, ahead of Dennis's BMC team-mate Cadel Evans and Tom Dumoulin (Giant-Alpecin).
"I know this climb quite well - but I didn't quite get the (leader's) jersey which is disappointing," Porte said.
"Full credit to Rohan, though. I gave it to him as much as I could and he didn't crack."
The fifth stage traditionally begins in the wine growing region of McLaren Vale and consists of three circuits through the vineyards and along Aldinga Beach, before two climbs up Willunga Hill.
Early race leader Jack Bobridge (UniSA) attacked from the opening kilometre, intent on staying ahead long enough to take King of the Mountain points on the first ascent of Willunga Hill.
He was joined by fellow Australian Jordan Kerby (Drapac) and New Zealander Greg Henderson (Lotto Soudal) with the three opening up a five-and-a-half minutes lead after 30 kilometres of racing.
The three leaders held on for more than 100 kilometres until Kerby dropped off the pace as they left Aldinga Beach for the final time.
The peloton, led by the BMC team, did all the chasing and slowly closed Bobridge and Henderson down, the Kiwi finally giving up at the bottom of Willunga Hill.
But Bobridge held on and crossed the summit 50 seconds ahead to claim the points.
He was soon overhauled on the descent and with 20 kilometres remaining the race was on in earnest. At the bottom of the final climb a group of about 40 riders remained in contention.
Orica GreenEDGE wound up the pace as they tried to set the race up for Daryl Impey, but Team Sky's Geraint Thomas took over at the front and increased the tempo.
All the main contenders were still in touch until the final 1.2 kilometres when Porte attacked with a withering burst of speed.
Evans, Dennis and Dumoulin went with him, but Evans cracked first and then Dumoulin fell away.
Dennis stayed in touch until 500 metres from the finish as Porte was left to claim his second Willunga stage in a row.
Results from the 151.5km fifth stage of the UCI Tour Down Under from McLaren Vale to Willunga in South Australia on Saturday:
1. Richie Porte (AUS - Sky) 3hr 37min 32sec
2. Rohan Dennis (AUS - BMC) at nine seconds
3. Ruben Fernandez (ESP - Movistar) +16
4. Cadel Evans (AUS - BMC) same time
5. Tom Dumoulin (NED - Giant Alpecin) s.t.
6. Domenico Pozzovivo (ITA - AG2R La Mondiale) +19
7. Tiago Machado (POR - Katusha) +24
8. Moreno Moser (ITA - Canondale-Garmin) +26
9. Gorka Izaguirre (ESP - Movistar) +28
10. Arnold Jeannesson (FRA - FDJ) s.t.
51. Geraint Thomas (GBR - Sky) +4min 9 sec
83. Jack Bobridge (AUS - UniSA) +8:45
106. Marcel Kittel (GER - Giant-Alpecin) +14:30
1. Rohan Dennis (AUS - BMC) 17hr 19min 09sec)
2. Richie Porte (AUS - Sky) at 2 seconds
3. Cadel Evans (AUS - BMC) +20
4. Tom Dumoulin (NED - Giant Alpecin) +22
5. Ruben Fernandez (ESP - Movistar) +24
6. Domenico Pozzovivo (ITA - AG2R La Mondiale) +31
7. Daryl Impey (RSA - Orica GreenEDGE) +38
8. Tiago Machado (POR - Katusha) +46
9. Gorka Izaguirre (ESP - Movistar) +52
10. Jarlison Pantano Gomez (COL - IAM) +53
42. Geraint Thomas (GBR - Sky) +5:44
60. Jack Bobridge (AUS - UniSA) +9:18
120: Marcel Kittel (GER - Giant-Alpecin) +50:18
King of the Mountain
1. Jack Bobridge (AUS - UniSA) 36 pts
2. Rohan Dennis (AUS - BMC) 34 pts
3. Richie Porte (AUS - Sky) 22 pts
1. Daryl Impey (RSA - Orica GreenEDGE) 39pts
2. Cadel Evans (AUS - BMC) 37 pts
3. Tom Dumoulin (NED - Giant-Alpecin) 36 pts