Geraint Thomas retained the overall lead at the Tour Down Under following a gutsy performance from Team Sky.
Thomas and his team-mates were able to defend the leader's Ochre jersey on a brutally tough stage in the Australian heat on an undulating circuit around Stirling.
At the finish there was a surprise winner in Tom Jelte Slagter (Blanco Cycling) who held off his rivals on the uphill drag to the line.
Thomas narrowly missed out on bonus seconds at the line with fourth, yet maintained his five-second lead while Matthew Goss (Orica-GreenEDGE) and Philippe Gilbert (BMC Racing) rounded out the podium on the day. Fourth also saw Thomas pull on the sprints jersey in addition to his lead in the mountains classification.
In temperatures of up to 38 degrees Celsius Team Sky spent the majority of the stage on the front, an impressive force which was put to the test by numerous attacks.
After the finish leader and Thomas said: "It was pretty tough out there. A lot of guys started attacking us from three laps out so the boys had to ride really hard. They did an incredible job today. They set a fast tempo and I can't thank them enough.
"In the final [Mathew] Hayman was with me until about two kilometres to go and then after that I just had to follow the wheels. I couldn't manage a podium finish which would have been nice to get a few more seconds but it was a tough day so it's mission accomplished I guess."
With a new rival emerging in the now second-placed Slagter Thomas added: "It's always going to be seconds in it and I think it's all going to come down to a big duel on Willunga on Sunday."
Explaining the conditions to Sky Sports Edvald Boasson Hagen said: "It was really hard and hot out there. The team did a really good job, especially Bernie [Eisel] who was riding mostly alone at the front the whole day. Hopefully we can keep fighting like this as a team.
"We have to defend the jersey and we've done a good job today. Hopefully we haven't expended all of our energy and we'll have something left, but it was tough for all the riders in the peloton today."
139km in the heat lay ahead as the riders left Unley for what many were describing as the toughest test of the race with six laps of a heavy stage around Stirling on the agenda.
The first job of the day for Team Sky was to control a surging peloton as the stage got under way, the race heading up the steep Mount Barker Road to the first categorised climb.
A group of 23 riders broke clear early on but in the end it was a two-man break of namesakes William Clarke (Argos-Shimano) and Simon Clarke (Orica-GreenEDGE) who went clear.
Thomas and Team Sky were alert at the first sprint point in Heathfield as Thomas nipped out to take third place and a single second to add to his race lead.
With the gap spinning out to 3:25 Team Sky set about pegging the duo, Bernhard Eisel again grinding away on the front for the third day running before the rest of the team took up the baton.
With 50km to go the race received a shake-up as numerous attacks tried to fire clear from the peloton, forcing Team Sky to re-double their efforts.
With help finally arriving from Lotto-Belisol a dangerous late move from Tiago Machado (RadioShack-Leopard) was snuffed out but at the line it was Slagter who claimed a breakthrough victory.
After the stage Sports Director Kurt-Asle Arvesen praised the riders, commenting: "It was a great team performance from the guys today. It was a chaotic stage and really hard with the heat close to 40 degrees. The pace was high right from the start and it was a really tough circuit. Almost like a world championships in a sauna!
"The team did really well to control things from kilometre zero – never panicking and never losing control. The whole peloton is tired after that and you could see at the finish it was only a small group that remained.
"Now it’s about resting up, taking on fluids and getting a massage ahead of tomorrow. It’s still really close on GC and a big fight. Hopefully tomorrow it will be an easier stage but we need to be prepared for everything."