Gullit: Chelsea group no picnic
The Blues, semi-finalists last season and runners-up to Manchester United in 2008, face Porto, Atletico Madrid and Cypriot minnows APOEL Nicosia for a place in the last 16.
But Gullit, who made 32 league appearances for the Stamford Bridge outfit before coaching them to the 1997 FA Cup, says that - despite avoiding Real Madrid and Inter Milan - Carlo Ancelotti's side have been handed a tough group.
"It's a tough group because Porto and Atletico Madrid are very good sides at the moment," he told This Is London.
"Atletico could be one of the dark horses for the competition. I saw them a couple of times this year and they impressed me, especially with the way they qualified so easily.
"The thing is with Porto they have experience of the Champions League and know how to survive.
"I don't think AC Milan's group is worse than Chelsea's. It will be tough for the teams in both groups.
"They will have to really dig in."