Lee Johnson has already added to his squad, with Alex Pritchard, Corry Evans and Callum Doyle joining the Black Cats in recent weeks alongside a host of signings for the under-23 team.
But there is plenty of work still to be done given nine players have already departed Wearside over the course of the summer.
And indeed, there are some clear gaps in the squad at present.
Full-backs remain a major concern, although academy graduate Denver Hume appears to be closer to agreeing a new deal. Johnson is also expected to try and sign another central defender, while striker Charlie Wyke is yet to be replaced.
The head coach says a number of factors have created a challenging market, but insists the club's patience will be rewarded.
"We've got a bit to do, no doubt about it," he said, speaking after the pre-season win at Hearts.
"It has been a tough market and I think we've done exceptionally well with what we've done.
"You say three signings but I 100% see it as five with McGeady and O'Nien, because they were in the open market.
"But we still have a lot of work to do, we know that.
"We clearly need a left back, a right back. We have got players who can play there, but we don't want to take players away from their natural position. We know that.
It has been a tough market because you've got GBE to account for, which means foreign players that used to be available are not.
"Then you've got the Premier League purchases, if you like, from the U23s and the lads who've been out on loan. We're willing to pay fees for these players but they often come with extremely high wages and often aren't willing to take a drop.
"Then you've got the talented players from lower levels who now command higher fees because they're English, and we do the same with any of our young English players.
"The pool of players is then quite small. You've got to get the right ones and we will get them, no doubt about it."