United have endured a hard summer transfer window as they have tried and failed to sign a host of defensive targets, with Tottenham centre-back Toby Alderweireld and Leicester's Harry Maguire among the names on their wish-list.
Last season's runaway champions provide the opposition at the Emirates Stadium as Arsenal begin a season without Frenchman Arsene Wenger in the dugout for the first time since 1996.
"They returned on Monday, trained Monday, Tuesday, Wednesday and today so you can imagine they are not really fit and ready but we have needs", Mourinho said.
"I think it's so hard now because it's only four hours until the end and I don't have news now", Pochettino told a news conference.
But outgoings have been put on hold for the past couple of weeks with the focus on securing incomings, with a new centre-back top of their wanted list.
In addition to no buys, Spurs weren't strongly linked very much with adding new players summer.
"The manager is obviously not happy about the signings he hasn't been able to make and not having certain players available on their pre-season tour, which isn't nice to hear if you are a young kid trying to make your mark on the fringes of the squad".
The window remains open to European clubs until the end of August, so there is still the possibility of players going out even after the English deadline passes. "He will make them better".
"I think it's so hard now".
Somehow, though, it appears the stakeholders didn't account for the World Cup.
"When I listen, when I read - not much but sometimes I do - it is hard to believe that we finished second because you [the media] are capable of making people who finished second look like they were relegated and capable of making people who win nothing and finish below us look like serial winners".
"The players from a year ago are responsible for the excitement, and then we brought in a few new players as an icing on the cake", said Klopp on the club's promising pre-season tour in the States.