The Dutch pundit told De Telegraaf via Voetbalzone: “When you get so many new players, it takes time before you have made a unit of them. They were still in full swing of that process.
“But you know how it works in top football. In the beginning there are always great stories about a new path that is being taken and that you get the time to build something up, but in the end the results always fall and stand.
"Even if you are a kid of the club."
The former Holland international struggled to break into a Blues team with John Terry and Ricardo Carvalho selected by Mourinho as his first-choice centre-backs. Boulahrouz was largely reduced to playing a limited bit-part role as a fullback.
On the choice of Thomas Tuchel as Lampard's replacement, Boulahrouz opined: “I don't know if that is the right choice. He played good football with Borussia Dortmund, but I am less enthusiastic about what he did with Paris Saint-Germain.
"Chelsea had gone down a certain path with Lampard and I wonder if Tuchel is the right man to take this further. In any case, there is a lot of quality in this group and it is up to him to get it out."
Boulahrouz, now 39, is a popular pundit in Holland. After leaving Chelsea, the former defender played in Spain, Portugal, Denmark and his native Holland, where he eventually hung up the boots in 2016 with 18 months to run on his Feyenoord contract.
- updated January 27