New Wolfsburg signing Diego believes his former club Juventus have made "huge mistakes" in the transfer market.

The Brazilian attacking midfielder returned to the Bundesliga just one season after joining the Turin giants from Werder Bremen.

Diego signed for Wolfsburg for a record transfer fee of 15.5 million euros last month, almost 10million less than Juve paid for him last summer.

"The transfer market campaign made by Juve is full of mistakes," said Diego in an interview with Sky Italia. "They have lost so much money as well as stars.

"I hope that in the future they will have a winning project with the understanding that the quality not only belongs to Italian players and that you cannot exclude foreign champions. You cannot win like that."

Diego believes Juve's general director Giuseppe Marotta is to blame.

Marotta took up the position at the end of last season when he left Sampdoria.

"(Juve coach Luigi) Del Neri was very clear with me, he said he wanted me to stay," said Diego. "On the other hand, Marotta was not clear.

"I always said that I wanted to stay and the coach always told me that he would have played me.

"If Marotta wanted to sell me he could have done it two months ago (instead of three days before the final day of the transfer window) as it would have been simpler and he would have found a better solution.

"The fact is that Marotta did not behave well with me or with other Juventus champions like (Mauro) Camoranesi or (David) Trezeguet.

"He does not have the experience to guide Juventus.

"Juventus should have been much stronger.

"The players that have left would have been useful to the next technical project."

Juve sold French striker Trezeguet to Primera Liga promoted side Hercules this summer while Italy international Camoranesi was sold to Stuttgart.

Italian pair Alberto Aquilani and Fabio Quagliarella were among the acquisitions made by Juve this summer.

Juve began the Serie A season last week with a 1-0 defeat to Bari.