Owen Farrell admits he will have to keep his head in Australia after momentarily losing it in the Hong Kong heat on Saturday.

The fly-half was perhaps lucky to escape punishment from referee Steve Walsh, an Australian, after punching his Saracens clubmate, Schalk Brits, just seven minutes into the Lions' opening tour match.

Walsh initially blew for a penalty against the Lions, before it became clear on the big screen replay that Brits was the main offender. Taking offence to Farrell pulling his jersey at a ruck, Brits blindsided him in the jaw with a sneaky shot. Brits was only yellow-carded, but he was later cited and will serve a three-week ban at the start of next season.

At 21, Farrell is one of the Lions' youngest tourists, and some have questioned if he is ready to handle the pressure of being the team's main creative force, with Jonny Wilkinson waiting in the wings back in Toulon.

Members of the Australian team watching the historic first Lions game in Hong Kong might already be hatching ploys if they suspect Farrell can be provoked. Warren Gatland, the Lions' coach, suggested it might have been a timely reminder to his players of the importance of keeping discipline, and Farrell was suitably contrite afterwards.

"When someone reacts to you, you try not to take a backward step, not just on this occasion but on every occasion," he said. "I just grabbed him, there was nothing in it and nothing in what happened afterwards.

"These are big games, every game you're going to play for the Lions is massive and to lose someone to the bin would be massive. You can't afford to do that. There's a fine line; you don't want to throw punches."

Perhaps more worrying was Farrell's overall performance. His kicking was excellent, but his handling was very poor and it was one bad pass that led to the Barbarians' try, making it 30-8 in the second half after Paul O'Connell and Mike Phillips (2) had gone over for the Lions. The team was markedly better when Jonny Sexton came on, stretching their lead through Jonathan Davies, Alex Cuthbert (2), Dan Lydiate and Alun Wyn Jones.

No-one will win or lose a place in the Test team after one game, with Gatland saying he will look at every player in the opening three matches, but Farrell knows he needs to improve

The match was played in temperatures at or near 30C, with humidity ranging from 70 to 80%. But Gatland insisted the trip to Hong Kong had been good for his players, likening it to training at altitude in that it might actually make them stronger in Australia's cooler conditions.

All three Scots played. Stuart Hogg certainly didn't look out of place at full-back and Stuart Maitland was unlucky not to get at least one try with his pace up the wings. The standout was Richie Gray though, playing in his first match since injuring his hamstring in March and seemingly near his best already. All three seem likely to be involved in the Tests, though perhaps not as starters.

Gatland declared himself happy with every one who played and said they had all "laid down a real marker", but he had been particularly keen to take a look at Gray. "We decided to leave Richie on because he's not played for about 11 weeks and he was dying out there in the end. We just wanted to get some rugby into him.

"It's been a good start to the tour, to get to have a look around Hong Kong and bond as a team without the intense interest that there's going to be over the next few weeks."

The temperature in Perth for the Western Force match on Wednesday should be around 10 degrees less, but the intensity will be ramped up more. Gatland will hope cooler heads prevail.