The 28-year-old keeper has made two appearances for his national side and was part of the Croatian squad that came third at the World Cup in Qatar.
However, Grbic's playing time for Atletico has been limited, as he has been forced to play backup to Slovenian international Jan Oblak.
According to Football Insider, Sheffield United manager Chris Wilder is actively pursuing a new goalkeeper during this month's transfer window as he looks to bolster his side's survival hopes, and The Blades boss has identified Grbic as a potential target for the position.
The report adds that the Croatian is currently in the last six months of his contract with Atletico Madrid, and the Spanish club is now open to selling him rather than allowing him to run down his contract and depart on a free transfer in the summer window.
A separate report from the Daily Mail mentions that Los Colchoneros may be willing to part ways with the player for just £2m.
It is understood that Wilder has also been keeping tabs on goalkeepers such as Kasper Schmeichel and Danny Ward.
The Blades' current keeper Wes Foderingham has played every minute of the current Premier League season and has conceded 49 goals in 20 matches while keeping only a single clean sheet in that time.
It is believed that Wilder sees Grbic as an individual that will introduce competition for Foderingham, who could drop in the pecking order as a result.
Grbic joined Diego Simeone's team in 2020 and has made a total of 14 appearances during his tenure at the club.
During his time in Spain, the Croatian shot-stopper has conceded 14 goals while
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