Sorry, but no.
There is a similarity regarding soccer in that the story involves two men who played international soccer during the same time period.
But there is no assured or proven connection. FR was a soccer player in Luxembourg in the 1960s, and yes, he has three caps with the Luxembourg NT. These were test matches and friendlies.
- 29 Jan 1967, Barcelona: Spain vs. Luxembourg, 5:0
- 20 Nov 1968, Copenhagen: Denmark vs. Luxembourg, 5:1
- 8 Dec 1968, Luxembourg City: Lux vs. Belgium, 0:1
From what I read about Johnny Warren, the two careers were in no way comparable, not even close. Luxembourg soccer was and for the most part still is amateur sports (today more towards semi-pro, but far from what it is in, say, France, Belgium, England).
FR was an aspiring and ambitious soccer player, debuting for the NT at the age of 19 and getting at least one good review for his defensive work against Belgium. He was about to sign a pro contract in Belgium, but that fell through due to injuries, so he buried the idea of a pro career.
JW on the other hand, according to Wikipedia: Captain of Australian NT. 42 caps, including the World Cup tournament in Munich in 1974. International contract in Britain, including media coverage. Coach. Commentator. Receives FIFA Centennial Order of Merit. MBE. Street named after him. State Funeral.
FR was not what you can call “a well known European soccer player”. He might have been relatively known in Luxembourg, but that's because the country is so tiny and people know about each other here. He surely wasn't known outside Luxembourg, and that's for the same reason: Nobody abroad knows much about Luxembourg. There definitely was no buzz around the Lux NT back in those days, not nationally, but much less internationally. (There is some attention for them today, after their narrow miss to qualify for the Euros.)
For scale: The average turnout for games in the first national soccer league in Lux for the season 2023/24 was 421. You read that right.
There is no connection involving soccer. That is a synchronicity, if you will. The FR connection, IMOO, is purely based on the events in Lux in the 1980s involving MC. Or do we really think that AKA had MB in the crosshairs back in 1980, leading him to pick out FR as a target to steal his identity in order to set up the soccer connection 17 years later? We still don't know why he used the FNR alias out of all he had in stock. And why it had to be Lux for MB. But JW had nothing to do with it.
However, I totally see that it is tempting, and it sparked my interest, too, in the very beginning: two international soccer players as the missing link. What a story. And it might even have been a big part of 7s motivation to fund a trip to Luxembourg in 2019. But there's correlation and there's causality.