Interim manager Benitez claimed the Stamford Bridge decision-makers who have halted contract talks with the England midfielder had no doubt about "his condition, his levels, his quality".
Benitez suggested owner Roman Abramovich and the board were analysing "different things", but did not go into more detail.
It is only possible to speculate what they might be but one could be the fact that Lampard is one of the highest earners at the club during an era of Financial Fair Play.
His age, 34, and recent injury record might also come into it but Benitez told BBC Sport: "For sure, he's a fantastic player, a great professional - there's no doubt about this.
"Also, when I talk to the people in charge, they are telling me the same, so nobody has any doubt about his condition, his levels, his quality.
"So the decision could be analysing different things, not just the quality of the player."
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- Roman Abramovich