'You could see he was happy': Alexandre Lacazette scores on debut in Arsenal win against Sydney

Alexandre Lacazette of Arsenal celebrates scoring a goal during the match against Sydney FC at ANZ Stadium on July 13, 2017 in Sydney, Australia.

Arsenal's record signing Alexandre Lacazette scored on debut in their 2-0 win over Australian champions Sydney FC on Thursday.

Lacazette, signed last week in a £52.5 million ((Dh250m) deal from Lyon, came off the bench in the second half to score Arsenal's second goal before more than 80,000 fans at Sydney's Olympic stadium.

Lacazette side-footed home to beat goalkeeper Andrew Redmayne from close range after captain Per Mertesacker had opened the scoring in the fourth minute.

"It's important that he gets that off his shoulders because you as a striker expect to score, so you could see he was happy," Arsenal manager Arsene Wenger told reporters.

"But overall what we look for basically is to play at a good pace and develop our collective game and for long periods in the game that was quite good for us.

"They gave us tough opposition, they tried for every ball and I would say at the end of the day their goalkeeper was man of the match."

Up to Lacazette's slick finish Redmayne, a one-time triallist at Arsenal, had denied them with a string of spectacular saves to give Sydney FC an outside chance of snatching a draw against the English Premier League club.

Arsenal got off to a dream start when defender Mertesacker latched onto an overhead kick off a corner from fellow German Mesut Ozil to put his team ahead in the opening minutes. Mertesacker pivoted and let fly to beat Redmayne from close range.

Youngster Reiss Nelson was lively down the right wing and troubled the home defence before he tired late in the half.

"All the youngsters did well; Nelson and Joe Willcock had a very strong performance, they are very young, just 18 years old, so that's very promising and they are English as well," Wenger said.

Sydney made few inroads into Arsenal territory but almost equalised when striker Matt Simon hit the side netting after Petr Cech made a low parry save off a Josh Brillante volley in the box.

Redmayne made a double save shortly afterwards and then flung himself to prevent Willock from scoring with three minutes to half time.

Nelson came close just after the resumption before substitute keeper Emi Martinez had to get down sharply to keep out Chris Zuvela.

Arsenal received a dubious penalty decision 10 minutes into the second half when Theo Walcott's shot hit the back of scrambling defender Sebastian Ryall but referee Shaun Evans signalled hand ball and pointed to the spot.

But Redmayne again came to Sydney's aid with a diving save to his right to keep out Danny Welbeck's spot kick.

"We made a mistake, we should have given them the ball back, it's always difficult to know how to behave, we should have just rolled the ball back," Wenger said.

"I don't know if Danny Welbeck saw it on video, but on the video it was obvious it was no penalty."

READ MORE: Mesut Ozil says selling Alexis Sanchez would hit Arsenal 'quite hard'

Wenger made mass changes midway through the second half, taking off all 10 of his outfield players and among his substitutes on came the club's new record signing Lacazette.

Redmayne again produced another acrobatic save to keep out an Alex Oxlade-Chamberlain free kick.

But Lacazette delivered the clinching goal when he finished off Alex Iwobi's cross from the right to find the net.

Arsenal play the second of a double-header of friendly matches in Sydney against Western Sydney Wanderers on Saturday before they head to China.