Former Dutch international believes that the absence of Lionel Messi in his side is the key behind Pep Guardiola's Manchester City struggles in the Champions League.
Messi and Guardiola won two Champions League titles together during his time in charge at the Nou Camp, however the Catalan boss has not reached a Champions League since 2011 - missing out with both his current side and Bayern Munich.
"Guardiola doesn't win the Champions League because he does not have Messi - and that makes a big difference, Guillit told BeIN Sports.
"He tried with Bayern, and came close each time, but never won it.
"At Barcelona, when games were tight, Messi appeared.
"Messi was vital for Guardiola's Barcelona in so many games.
" You cannot buy a team that does that. But I do feel sorry for him as I see his passion to win it."