The defending champions lost 1-0 to Manchester City in their last Premier League game before the international break after Kevin De Bruyne scored a second-half winner at Stamford Bridge.
Chelsea signed off on September six points behind Premier League leaders Manchester City and Manchester United following two defeats in their opening seven games.
The west London side have won the Premier League title in two of the past three seasons under Jose Mourinho and then Antonio Conte but face a tough assignment this term given the strength of the two Manchester clubs.
Indeed, Manchester City have already put down a marker with a 5-0 win against Liverpool at The Etihad before a narrow 1-0 victory over the title holders at Stamford Bridge last time out.
Former Manchester United captain Robson believes the Manchester clubs would be foolish to discount Chelsea from the title equation gives their experience of winning the title, despite the Blues’ shock loss to Crystal Palace on Saturday.
“I think we will definitely be there challenging,” Robson told Sky Sports before this weekend’s fixtures.
“I think Manchester City are looking really exciting and powerful.
“Even though Chelsea have had a couple of defeats so far, you can’t write them off, because it’s a long, hard season.
“But I think United, right from the start of the season, have put themselves in a position where we can definitely challenge whoever is going to win the title, or whether we win it ourselves.”
Manchester United have a manager in Mourinho who has won the Premier League title on three occasions during two different spells with Chelsea.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news