Diego, 24, steered Werder to their first UEFA Cup final on Thursday, scoring once in their 3-2 win over Hamburg SV.
"There has been a meeting between Juventus and Werder. But we cannot confirm that an agreement was reached," Werder managing director Klaus Allofs said on the team's website.
The Brazilian will, however, miss the UEFA Cup final against Ukraine's Shakhtar Donetsk in Istanbul on May 20 after being booked for an altercation with Hamburg's Alex Silva.
"We will badly miss Diego in Istanbul," Werder coach Thomas Schaaf told reporters, adding that he was "furious" at referee Frank De Bleeckere for booking the Brazilian.
"He is an exceptional player. He helped us to get to the final and I hope the team can bring something back for him."
The gifted playmaker has been the driving force in Werder's run to the final, finding the net four times in two legs to oust Italian side Udinese in the quarter-finals.
Diego blamed compatriot Silva for the booking, which will see him miss Bremen's biggest match of the season.
"Unfortunately I cannot change things," Diego said. "(Silva) swore at me. I did not respond, I was pushed and then got booked."
"But we did a great job and we have a big enough team to win the cup in Istanbul," the 24-year-old said.
