The World Cup-winning Argentine has been linked with a move to Al-Hilal after he was suspended by Paris Saint-Germain after travelling to Saudi Arabia without the club's permission.
Al-Hilal are preparing to take on Japan's Urawa Red Diamonds in the second leg of the Asian Champions League final in Saitama, north of Tokyo, after a 1-1 draw in last week's opener in Riyadh.
Diaz refused to comment on reports that Al Hilal have already made Messi a multimillion-dollar offer, saying his team are thinking only of winning a record fifth Asian title.
"Now we are focused on the game," the Argentine said Friday.
"We have a final, and after the final we will see what's going to happen."
Messi's future at PSG was plunged into doubt on Wednesday after he was suspended for two weeks for his unauthorised trip to Saudi Arabia to fulfil a commercial role.
He is out of contract at the end of the season, with a host of clubs including Barcelona reportedly keen to sign him.
Al Hilal's Saudi rivals Al-Nassr made global headlines when they signed Cristiano Ronaldo (38) in December on a deal to June 2025.
Al Hilal are one of Asia's most successful clubs and scored three goals past Real Madrid in a 5-3 loss in the Club World Cup final in February.
Urawa playing to win
Diaz said his team are ready to overcome Urawa and win a third Asian title in four seasons.
"This is a very experienced team and we have played in many situations like this," he said.
"We are strong and we are looking forward to winning the trophy."
Al-Hilal will be without injured captain Salman Al Faraj and star winger Salem Al Dawsari, who was sent off late in the first leg for kicking out at Urawa's Ken Iwao.
Diaz said he was confident that "no matter who replaces them, they're going to do well".
"We were not expecting to miss two key players but we have a full squad and all the players are ready," he said.
Al-Hilal and Urawa are meeting in the final of Asia's premier club competition for the third time in six years - Urawa came out on top in 2017 but Al-Hilal got revenge two years later.
Away goals still count as a tie-breaker, giving Urawa a slight advantage as they prepare to play in front of close to 60,000 fans at Saitama Stadium.
Urawa striker Shinzo Koroki, who scored a second-half equaliser in Riyadh, said the Japanese side would not be playing for a draw.
"We need to get rid of the idea that a goal-less draw will be OK for us - we're at home, with about 60,000 fans behind us," he said.
"We need to make sure they don't score, and get a goal ourselves and win the game."
