Finn Russell is a few months older than Allan, now Tommaso in Italian colours, but was hugely impressive in a rare Pro12 opportunity coming off the bench as he steered Glasgow to a come-from-behind victory in Cardiff at the weekend.
While Allan moved to Perpignan, and got plenty of first-team chances that propelled him into the Italy team, 21-year-old Russell has found it hard to make the breakthrough at home with the two players vying for the Scotland No.10 jersey above him in the pecking order.
His performance on Saturday encouraged coach Gregor Townsend to say: "I was really pleased for Finn that he got a shot to play at this level, if he plays like that then he'll get more opportunities.
"Finn looked really confident, he stepped up at first receiver and made a break with his first touch.
"Those kicks were important for us, which is what you want from your players - playing with confidence, taking the initiative, showing work-rate off the ball. We have strength in depth in a number of positions and fly-half is one of them."
Russell has been picked out as a young Scottish talent to nurture, coming up through the ranks at Stirling and Falkirk, sent on a scholarship to New Zealand and now with Ayr and Glasgow.
His progress has been slower than Allan's, something which says more about the lack of strategic planning at the top of Scottish rugby than it does about his talent.
Allan was kept on the bench for Scotland Under 20s by a combination of Edinburgh's Harry Leonard at 10 and Russell at 12. Leonard's progress has been slowed, partly by injury, but sitting on the bench behind the more experienced South African Carl Bezuidenhout at the weekend hardly helps Scottish rugby.
Whether Russell should have been moved to Edinburgh rather than bringing in a South African is something for the powers-that-be in Murrayfield, but the current solution does not seem the best one.
Instead, Russell has signed a new contract at Glasgow and is set to try to push his way past the current Scotland No.10s Duncan Weir and Ruaridh Jackson. He is looking forward to Townsend giving him more opportunities.
"It is great to hear that from your coach, especially with the Scotland guys away and a couple of games coming up, so it would be good to get some chances to show what I've got before the Scotland guys come back," said Russell, who landed four our of four kicks at goal in Cardiff.
"It was brilliant. A fast game on a good surface like that is the sort of rugby I love. The breaks were thanks to the other guys setting it up and the kicks only come from the forwards setting it up.
"In the U20's I played at 12 so I wouldn't say I kept Tommy out of the side, but as a back up 10 it was easy for me to switch if it was needed.
"Tommy got lucky, he got a chance and he took it. He's playing well. If you get your chance then you have to take it. Hopefully I will get a chance in the next couple of weeks so we will see what happens there. I have just signed a contract with Glasgow, it is great to be at the club. It is tough having two internationals in front of you but I will keep chipping away.
"I got my chance and hopefully I'll get another one. We are making Gregor make a decision about who he wants to play, rather than just a case of the internationals coming back."
If Townsend has some thinking to do in Scotstoun, they should be burning the midnight oil in Murrayfield working out how to ensure Scottish talent like Russell can get the playing time in Scotland they need to fulfil their potential. Watching Allan in action in Rome should focus minds.