Sunderland owner praises Richard Hill and Tony Coton for 'fantastic' work during the transfer window
The Black Cats signed 12 new players over the summer, some of whom were out of contract.
Others, like Chris Maguire and Tom Flanagan, weren't at the end of their previous deals, but still secured permanent moves to the Stadium of Light.
According to Donald, huge credit must go to new head of recruitment Coton and head of football operations Hill, who both followed Donald to Wearside earlier this year.
Following Sunderland's 3-0 victory over Southend, which saw Jack Ross' side move to within three points of league leaders Portsmouth, Donald tweeted:
"It is one thing picking up players out of contract and we have done well there. In Flanagan and Maguire though we have got them out of contracts without paying fees. Huge credit to @richhill11 & Tony Coton they r doing fantastic jobs behind the scenes for everyone @SunderlandAFC"
Magurie, 29, scored his fifth goal of the campaign against Southend following his arrival from Bury, and the forward has quickly become a popular figure with supporters.
After missing the first part of the season through injury, Flanagan, 26, has also become a key player for the Black Cats.
The 26-year-old centre-back has started the side's last seven league games and helped Ross' men keep three consecutive clean sheets.