Whereas potential outgoings have dominated much of the Arsenal transfer talk ahead of the next window, recent reports suggest that the club could be on the verge of making a significant addition to their squad.
The defensive midfielder has made 35 appearances for Atletico across all competitions this season and was widely praised for his performances against Liverpool in particular as Diego Simeone's side dumped the Champions League holders out of Europe.
Here, Sports Mole looks at how Mikel Arteta's side could look if they are able to sign Thomas ahead of the 2020-21 campaign.
Thomas is the type of player Arsenal fans have been demanding for years - a defensive midfielder capable of breaking up play, launching attacks and providing more steel to the spine of the team.
Before the coronavirus lockdown Arteta usually opted to play Dani Ceballos alongside Granit Xhaka in that role but, with the loanee expected to return to parent club Real Madrid before moving elsewhere this summer, there is likely to be a vacant place alongside the former captain.
Xhaka himself appears to have rescued what at one stage looked like an irreparably damaged Arsenal career, re-establishing himself above Matteo Guendouzi in the pecking order.
With Thomas adding solidity to the Arsenal foundations, the Gunners will hope to keep hold of those who can take full advantage of that further up the field - namely Pierre-Emerick Aubameyang and Alexandre Lacazette.
Aubameyang is the priority and with clubs' transfer plans being affected by coronavirus it is perhaps more likely now that he will still be at the Emirates in 2020-21, regardless of whether he agrees a new deal before that.
Lacazette's place in the side is in question considering Eddie Nketiah was preferred by Arteta in recent months, while Gabriel Martinelli is another youthful option up front to provide yet more competition for places.
Mesut Ozil again looks like he is going nowhere and would still make a full-strength XI, and the presence of Thomas behind those attackers could mean that Arteta is able to take even more risks by playing all four of his 'flair' attackers, Nicolas Pepe completing the quartet.
At the back, Kieran Tierney is expected to be the first choice when he recovers from an injury-plagued debut campaign at the club, while a lack of other options means that Hector Bellerin is still the best bet on the opposite flank.