Indeed, for most League One clubs, the significance of the business done on Monday may not become apparent until Deadline Day number two.
Owing to the shortened summer and the ongoing uncertainty of the pandemic, UK clubs opted to put in place an internal window that extends deeper into October.
Past Monday, EFL and Premier League clubs will be able to do business with each other until October 16.
Monday, then, is likely to be key in determining the transfer chain that will follow.
The loan situation
The business that Premier League clubs conclude will have a major knock-on effect, determining which players make their Premier League squads and who will be available for a domestic move, whether it be permanent or on loan.
Those decisions will trickle down to the lower leagues and it is here that the day may have some relevance for Sunderland.
Phil Parkinson still wants to add one or two players to his squad, with cover and competition at centre-back and left wing-back the main priorities.
The Black Cats boss has cut a relaxed figure when discussing transfers in recent weeks.
He is happy with his squad in the main and even in the positions where extra depth is welcome, he has options in the team currently performing to a good level.
Patience, then, is not an issue.
The Black Cats boss revealed last Thursday that a potential target had visited the Academy of Light last week with a potential view to a deal, but the results of a physical assessment meant this has been 'put on the back burner'.
That brings the loan market back to the fore, and though it's one he is cautious about given the homegrown youngsters at his disposal, there are long-term targets he would consider.
“We know what we'd like to do and it's more and less what I say all the time,” Parkinson said.
“We did have a player up for an assessment this week but medically he wasn't quite right, so we've put that on the back burner.
“There are one or two loan players who we identified right at the very start of the summer, but whose parent clubs are still umming and ahing about whether they are going to let them out.
“And with the loans, any young player we've got to be sure that they are significantly better than what we've got at the club.
“We've got Jack [Diamond], we've got Dan [Neil], Benji [Kimpioka] has signed his contract.
“We see a route for these players into our first team, so it's pointless bringing them in [unless they will play].
“We're looking, but we've got a decent squad and the competition is decent at the moment.”
Monday and the days that follow could be important in determining their availabilty or otherwise.
The probablility of Sunderland concluding any deals on Monday itself is slim.
Parkinson himself noted last week that the break which follows the EFL Trophy clash with Carlisle offers a good opportunity to take stock and assess before making their final moves.
The international targets Sunderland have monitored
Of course, it is the last day in which Sunderland could move for any international targets.
We have seen this summer that the club have taken an active interest in any players, particularly those under the age of 21 who would not count towards the salary cap rules, who could provide value.
The most high profile of those was Mateo Bajamich, though from early on in those talks, Parkinson publicly hinted strongly that he expected Sunderland to be outbid.
He also stressed that this deal was something the club viewed as an opportunity, rather than a necessity. In short, don't necessarily expect the money to be spent regardless.
"We get a lot of players pushed to us and we spend a lot of time going through him in our system,” Parkinson explained.
“Our analyst will look at them and then say to us, 'we really need to look at this one'.
"He was definitely in that category, U21, has pace, so we looked at him.
“But it was always going to be difficult to do a deal because the minute a couple of clubs are in for a player, the price goes up to a level that becomes a little bit too much.
“I'm speaking to agents and clubs all the time about U21 players and players that could become available.
“We'll make sure we look at everything but we're pleased in general with what we've got.”
It's a fascinating topic as many supporters are still eager to see some pace and dynamism added to the front line, attributes that Parkinson clearly feels Bajamich possessed.
Speaking on Thursday, Parkinson admitted more pace would be welcome but also namechecked Jack Diamond and Benji Kimpioka as two players who could bring that to the table.
He also noted that there 'was no hiding away from the fact' that the announcement that crowds could have to wait six months to return to Stadiums was also likely to have an impact.
A situation that needs resolving
One potential deal many supporters will be keeping an eye on is that of Aiden McGeady.
Sunderland are clearly keen to offload the winger, who has no place in Parkinson's plans. Past Monday, the market becomes very limited in terms of finding a potential suitor.
The situation has been complicated significantly by a calf injury that means McGeady is still weeks away from full fitness, even if he did return to play some part in U23 sessions last week.
Parkinson would welcome the chance to draw a line under this particular saga, but is not clear where there is substantive interest at this stage or indeed whether McGeady would welcome it.
Settled in the area and with time to run on his deal, the ball remains in his court.