Alves comes off contract in June and is expected to move to PSG this summer.
"Dani Alves has set the bar high at Barca. It will be very difficult to find a fullback to match him. He will still be in football for a long time," Donato told Sport.
Former Sao Paulo fullback Douglas is regarded as Alves' successor at Barca.
But Donato adds: "I do not know Douglas, I do not follow Brazilian football much, I've seen only a few games.
"When he joined Barcelona I was surprised, but some have seen something in him."