The future of the 34-year-old is unclear, with contradictory speculation in midweek over whether the midfielder will be offered a new contract to extend his 12-year stay beyond this summer.
Benitez said: "The last two months he's scored eight or nine goals - really pleased.
"If he scores 20 goals and breaks the record, I'll be really pleased."
Benitez would not be drawn on Lampard's future when asked how long the midfielder can continue to play at the highest level, referring only to next week's Europa League clash with Sparta Prague.
"If he's available for Thursday, I will be really pleased," the Spaniard said.