By SABC Sport
30th August 2024
The midfielder has travelled to Italy ahead of the transfer deadline to complete a deal understood to be worth 25.4m.
McTominay's departure paves the way for the arrival of Manuel Ugarte from Paris St Germain and Ten Hag believes both deals are close.
He told a press conference: "I can't tell you more than you already know, it's not completed yet.
"We expect it (to be completed), but I can't confirm it now."
McTominay's move to Napoli would end a 12-year association with United since joining in 2012.
He made his senior debut for the club against Arsenal five years later and became a regular in the United squad, amassing 253 appearances.
Ten Hag admitted McTominay's switch would present mixed feelings, but believes the transfer is necessary according to financial rules.
"It's a little bit mixed, I'm very happy for him," Ten Hag said.
"It's also (a good deal) for us, but it is mixed because I wouldn't prefer to lose him because he's Manchester United in everything.
"He was so important for our team, for Manchester United, but unfortunately it's the rules.
"We have to discuss the rules, when you have to sell and obviously homegrown and academy players bring more value, that's not the right thing to do.
"But I think for everyone, for all parts it's a good deal, for Scott he's happy with it, for Napoli a very good player, but also for us."
Ten Hag also revealed he expects Jadon Sancho to stay at Old Trafford beyond Friday's deadline.
The winger's future at the club has been in question since falling out with the manager 12 months ago.
He spent the second half of last season on loan with Borussia Dortmund before resolving his differences and returning to United.
So far, Sancho's only appearance this term has been as a substitute in the Community Shield and he has not featured in their Premier League matchday squads, with Chelsea rumoured to be interested.
When asked if he expected the 24-year-old to stay at Old Trafford, Ten Hag said: "As I know, yeah.
"He's playing in our squad, we're happy with him. We need a good squad, we need depth in the squad.
"We have to play many games until January. The new format of Europe, after the break we will play every third day. We need options."
Up next for United is a meeting with bitter rivals Liverpool at Old Trafford on Sunday.
Ten Hag confirmed Mason Mount will be the only absentee and provided an update on Rasmus Hojlund, who has been sidelined with a hamstring injury.
"We have to see how he develops and how he can progress during the break to get match-fit," Ten Hag said.
"He returns on the pitch, but it will take a while before he's up. He needs to also build some fitness."