Atletico Madrid are planning to take legal action against Barcelona after it emerged the Catalan giants had negotiated with the France international in November before trying to sign him in March.
Griezmann has already confirmed his decision to leave Atletico, where he was won a Europa League, a UEFA Super Cup and a Supercopa de Espana, with Barça thought to be best placed to capture his signature.
However, in information revealed by AS, Griezmann apparently negotiated with the 2018/19 La Liga winners when Atletico still had plenty to play for.
By the end of November, Atletico were two points behind then league leaders Sevilla, with Barcelona a point ahead, while in March they already had a two goal lead to take to Juventus in the Champions League round of 16.
Los Rojiblancos ultimately finished second in La Liga and were dumped out of the CL by Juve thanks to a hat trick from Cristiano Ronaldo.
However, they are yet to make a firm decision over whether or not to take legal action against the Catalan giants and want to study the available information closely before deciding whether it warrants further exploration.
Griezmann has a contract with Atleti until 2023 but his release will decrease from €200m to €120m in July. Reports regarding his future have been opaque, with Mundo Deportivo claiming Barca remain desperate to sign him, while Marca state Barca chief Josep Maria Bartomeu still has concerns over the deal.
Griezmann managed 15 goals and nine assists in La Liga this season, his worst combined haul since joining Diego Simeone's side, and played a major role in France winning the World Cup last summer.