[5] Initially, Gajić saw little playing time[5] as he was the team's second choice to starting right back Youssouf Sabaly.

[6] Although Red Star qualified for the 2019–20 UEFA Champions League, coach Vladan Milojević and Red Star's management opted not to register Gajić in their 23-man Champions League squad, ultimately choosing Marko Gobeljić as the starting right-back.

[7] On 17 June 2022, Gajić signed a three-year contract with Russian Premier League club CSKA Moscow.

[10] In May 2017, head coach of the Serbia U21 side Nenad Lalatović included Gajić in the final squad for the 2017 UEFA Under-21 Championship in Poland.

[11] He made his debut for Serbia national football team on 24 March 2021 in a World Cup qualifier against Ireland.