The winger had endured a torrid time at United after falling out with ten Hag and spent the second half of last season on loan at Borussia Dortmund.
However, Sancho appeared rejuvenated as he made his Chelsea debut as a substitute in a 1-0 win away to Bournemouth.
Sancho provided the assist as Christopher Nkunku scored the only goal of the game late on.
Enzo Maresca aimed a subtle dig at Manchester United manager Erik ten Hag after Jadon Sancho impressed on his Chelsea debut
Maresca suggested after the game that Sancho 'needs love' in order to be at his best.
Speaking in his post-match press conference, as reported by BBC Sport, Maresca said: 'Jadon was good, Joao [Felix] was good, Tosin was good & Christo [Nkunku] was very good. We decided to use Christo as a No 9 as he is good in the box'
'I have the feeling Jadon needs love'.
Sancho will be hoping for a fresh start at Chelsea and it will be intriguing to see how much of an impact he can make this campaign.
The 24-year-old was banished from United's first team last year when he hit out at Ten Hag after being criticised over his performances in training following a defeat against Arsenal.
Sancho said he was being made a 'scapegoat' and refused to apologise to Ten Hag, who said their relationship couldn't be repaired unless an apology was issued.
Sancho appeared to be back in favour as he featured for United in pre-season after returning from loan, but he subsequently ended up departing.