The Queensland Reds flyhalf played 40 minutes in Saturday's 29-28 Super Rugby AUS loss to the visiting Western Force at Ballymore.
It was Lynagh's only chance to impress Wallabies coach Les Kiss before he names the squad to face South Africa in Perth this month in Canberra on Monday.
Kiss, already in Canberra ahead of Sunday's other pre-season clash between the ACT Brumbies and NSW Waratahs, had assistant and former Reds staffer Jonny Fisher in the Ballymore stands.
There will be at least one new playmaker in that squad after fellow Reds No.10 Carter Gordon broke his leg in the side's last Test against Argentina in Mendoza.
There was some wobbly in-game kicking on Saturday, but Lynagh was perfect off the tee from three conversion attempts, and importantly ran into contact and probed the Force line with confidence.
Calf, hamstring and concussion setbacks have plagued the No.10, who started in all three Tests against the British and Irish Lions last year but has barely been sighted since.
"It was a great feeling getting back out there on the footy pitch, it's been a tough 12 months," said Lynagh, who came off the bench just once for the Reds all season.
"I didn't have a lot of expectations coming in, didn't want to overplay my hand, just be physical."
Lynagh has put on several kilograms in pursuit of some durability that has been lacking in that position at Test level in recent years.
"I felt like I was a bit more physical, confident in contact and felt a lot quicker and sharper, I just need to get a bit fitter," he said.
It was Vern Cotter's first game at the helm for the Reds after the New Zealand mentor took over from Kiss.
"Vern's great to be around and learn from," Lynagh said.
"Very fair, hard on you, but he gives you your kudos when you do something good. It's a great balance."Â
Harry McLaughlin-Phillips kicked just two-of-five conversions but ran the ball confidently as he pushed his own case for a Test call-up in his first Force minutes since leaving the Reds.
Force star Zac Lomax, playing in the No.13, was impressive in the air, collecting high balls in traffic and finding offloads to surely raise the eyebrows of Wallabies coaches.
The Reds, who lost Josh Flook to a lower leg injury, led 28-12 but got sloppy to give the Force a way back.
Kurtley Beale's injection helped pry that open and the visitors sealed the comeback win, McLaughlin-Phillips nailing the conversion after replacement hooker Albert Alcock mauled over in the 82nd minute.
