However, there was no return to form for Ravi Bopara who managed just six off 13 balls on the day he was surprisingly included in England's 15-man Champions Trophy squad.
After failing to reach double figures in two innings during the Championship victory over Hampshire this week, Bopara again departed early after being bowled stepping forward attempting to attack left-arm spinner Danny Briggs. That was a blow to Essex but Napier ensured they made a defendable total.
Fresh from his match-winning 78 not out in the Championship clash between the counties, Napier smashed 50 from 29 balls to provide much-needed momentum to the innings.
He strode to the wicket in the 31st over with the score on 143 for five and he was soon despatching Briggs for six.
He was to deal out the same punishment to Chris Wood and also helped himself to five fours as the visitors struggled in vain to stem the flow of runs.
Keeping Napier company was Greg Smith, the pair adding 93 in only 51 balls. Smith, not to be outshone, scored 47 from 43 balls with a six and six fours before he was bowled by Wood in the 39th over. Napier departed to the last ball of the innings, caught in the deep off James Tomlinson.
Earlier Rob Quiney struck 71 from 85 balls before he was bowled by medium-pacer Hamza Riazuddin having struck six fours and an on-driven six against slow left-armer Liam Dawson.
Quiney shared in two half-century partnerships, the first with fellow opener Tom Westley (34) who unleashed several well-timed drives before being stumped by Adam Wheater against Briggs with the total on 67.
The second featured Mark Pettini (21) who was caught in the deep immediately after Quiney's dismissal, the pair adding fifty.