The 18-year-old Dubliner benefitted from a deepening injury crisis in Liverpool's defence, with Joel Matip's absence thrusting him into the senior squad for the visit of Manchester City to Anfield in the Champions League.
Masterson didn't make it onto the pitch but soaking up the electrifying atmosphere as he watched his teammates thump City would have been an invaluable experience.
Just three days, Masterson was involved with Jurgen Klopp's first-team once again, taking a place on the bench for the scoreless draw with Everton in the Merseyside derby.
Again, the former Lucan United man wasn't called into action by the German but he did leave Goodison Park with an exciting souvenir: Seamus Coleman's shirt, as per Nathan Murphy.
https://twitter.com/nathanmurf/status/982626742190866433
Coleman played the full 90 minutes for Sam Allardyce's side but was unable to guide the Toffees to a rare derby victory over their rivals.
The Republic of Ireland captain will have been encouraged to see his young compatriot on the bench for the Reds, though. Masterson's emergence this week is a measure of his progress through the youth ranks at Anfield and it may not be too long before we see him make his senior Liverpool debut.
Masterson was one of four teenagers on the Liverpool bench, with Trent Alexander-Arnold, Rafael Camacho and Curtis Jones also part of the squad.
Although a Champions League quarter-final against Manchester City and the Merseyside derby may have been too intimidating for Masterson, but Klopp's quotes this week suggest the Dubliner remains very much in his manager's thoughts.
"I've said many times about young players that it's not about getting the opportunity, it's about being ready for the opportunity," said Klopp.
"Conor was last year in the U-18s and is in his first year with the U-23s - (he is) still a very young lad. It's a completely different experience.
"You have the use the next generation, they are there, really talented boys, and I'm always ready for using them but in the right games in the right moment."
Even though he hasn't managed to gain any competitive minutes, this week has been one to remember for Masterson, and getting Coleman's shirt was the icing on the cake.
https://twitter.com/empireofthekop/status/981841481769082881
