Jaros has not been part of a matchday squad for Liverpool since the 1-1 draw with FC Midtjylland in the Champions League in December 2020.
That was his fourth time warming the bench for Jurgen Klopps side, but in almost three years between then and now, he has rarely been involved.
Instead, there have been loan spells with St Patricks Athletic, Notts County and Stockport for the Czech goalkeeper, typically training with the U21s otherwise.
A call-up to the first-team squad for pre-season in Germany brought a cameo against Karlsruher SC, but he was then cut for the tour of Singapore.
Seemingly behind Adrian and Marcelo Pitaluga in the pecking order as backup to Alisson and Caoimhin Kelleher, there was surprise when Jaros was then included in Liverpools Europa League squad.
But there are two explanations for his involvement, in line with UEFA guidelines for squad registration.
Firstly, with Adrian omitted from the squad to free up a List A slot for Ben Doak, Liverpool were required to register three goalkeepers.
A minimum of two of those three must be registered on List A, with any further additions via List B (reserved for eligible players aged 21 or under).
The decision was made to include Jaros along with Alisson or Kelleher, presumably to avoid any availability issues further down the line.
Furthermore, having joined the club in 2017 and spent more than the minimum of 36 months on the books before, between and after his loan spells, the 22-year-old qualifies as club trained.
For clubs to name a full 25-man squad for the Europa League, a minimum of eight players must be locally trained and at least four of those club-trained.
Jaros qualifies as club-trained along with Kelleher, Trent Alexander-Arnold, Joe Gomez and Curtis Jones, with Klopp otherwise restricted to 17 foreign players including Doak.
In short, then, the young goalkeeper was included as cover for Alisson and Kelleher because his inclusion was free due to club-trained status.
Whether or not Jaros is ultimately involved against LASK, Union-SG and Toulouse, or perhaps Pitaluga is called up instead, registering him was just common sense.