Sancho was targeted by Ole Gunnar Solskjaer in the most recent transfer window but was hesitant to pay the £108 million asking price demanded by Dortmund.
The German side gave United until 10 August to make the deal in an attempt to end the transfer saga, but talks were ongoing up until the window closed earlier in October.
This season has seen Sancho only score once in six matches in their 5-0 victory over Duisberg. Favre believes that the unsettling over the summer has impacted the 20-year-olds performance and contributed to his slow start to the season.
Favre said: “Every player has slow periods. There was a lot of talk about Jadon during the summer – something like that can be a factor.”
Sancho was also involved in a Covid-19 breach during his most recent call-up with England as he attended a party in the run-up to international fixtures.
Dortmund were still able to make a strong start in the Bundesliga, winning four of their opening five matches. However, they find themselves down in the Champions League after losing to Lazio in their opening game.
Favre has said that he is not worried about the young player, claiming that dips in form are inevitable ahead of their European tie against Zenit.
He added: “No player is consistently in top form for an entire year, that’s impossible. You have to accept that.”
United have still not given up on signing Sancho yet though, and it has been speculated that they may also be after another Dortmund star, Erling Haaland, in a £176 million raid of the Bundesliga team.