Chelsea - Man Utd: Potter expecting tough test against improved United
Potter, who left Brighton to take over at Chelsea last month, oversaw a 2-1 win against United in Erik ten Hag's first league game at the helm back in August.
United have bounced back impressively since that loss to occupy fifth place in the table with 19 points from 10 games, just a point behind Chelsea who they meet at Stamford Bridge on Saturday.
"It wasn't a great start but they've battled back, got points and are playing well. It will be a tough game," Potter told reporters.
"They've changed a bit how they build up, bit more direct but at the same time they have the quality. They have the threats of (Marcus) Rashford, Anthony, (Jadon) Sancho, (Bruno) Fernandes. But they've adapted more to each other."
"They have galvanised into an impressive team. We are looking forward to it."
Potter, who has yet to taste defeat in seven games across all competitions, said it was too early to tell whether the team were playing in his image but credited the players for notching up three wins in four league games under him.
"Six weeks is a short time to really (understand the) true personality of a team. They've understood the challenge, they've been brilliant," he added.
Potter added that England right back Reece James (22) and France midfielder N'Golo Kante (31) were both dealing with the disappointment of missing the World Cup in Qatar after picking up injuries.
"(James) is in a brace for four weeks to stabilise the knee, then it's rehab. That will take around eight weeks. That's the latest," he said.
"They are human beings. The reality is, I've got nothing to say that will make it any better for them. You have to focus on the things you can control, rehab, go day to day."
Midfielder Conor Gallagher (22) could return against United after being withdrawn just 15 minutes into Chelsea's goalless draw against Brentford in midweek due to illness.
"Conor trained today so we will see how he is over the 24 hours," said Potter.