Although Vijay Mallya concedes Force India have struggled on the new Pirellis, he says the tyres aren't solely to blame for the team's poor run.
Having made a flying start to the Championship, Force India have netted just two points in the last four races and only ten since the new tyres were introduced at Silverstone.
The team's woes were compounded at Monza when Paul di Resta retired on the first lap while Adrian Sutil wasn't even knocking on the door of the top-ten, down in 16th place.
Mallya, however, says not all Force India's troubles in Italy, which also saw them suffer their worst qualifying performance of the season, were down to the tyres.
"Right through the [Italian Grand Prix] weekend we were struggling at a track that is supposed to be friendly for us," he told Autosport.
"We have done well there in the past, but for some reason we just could not find the pace and could not optimise the tyre performance. We have never been so badly off in the recent past.
"We tried a few things differently in the race, which we didn't do in practice and qualifying, and we were pleasantly surprised when Adrian [Sutil] got some pace - but that is no comfort. It is the end result that matters.
"We have to learn a lot more about the behaviour of these tyres, and hopefully we will get on top of it before Singapore, which is also a track that is friendly towards us.
"But we don't have any excuses for Italy - we were simply not good enough."
The team owner, however, does believe that part of Force India's recent troubles are down to Pirelli's changes.
"The car is different to last year. It was designed and constructed for 2013 with the tyres we had prior to Silverstone.
"We performed really well until then and after that we struggled when the tyres changed. It is a fact; not an excuse."
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