But once in their stride, Napier weren't going to give a centimetre.
Centreback Aaron Jones levelled with about 18 minutes gone, prodding home captain Bill Robertson's cross.
Ten minutes after the restart, Andy Bevin was impeded in the box so midfielder Cole Peverley scored from the penalty kick.
Eight minutes later it was 3-1 when Harley Rodeka's dainty header dropped at Bevin's feet and the returning striker had time and space to tap the ball in.
Bevin then scored the goal of the match, running at the timid defence and drilling the ball past Upper Hutt keeper Chris Campbell for Napier's fourth.
The Rovers looked more assured than they have done recently, passing and crossing generally at someone's feet or head.
Asked if it was one of the team's best wins south of Tararua, Hastings replied: "I think so. Not only the result but how we won. I thought we knocked the ball around very well at times.
"Even though it was one-all at halftime we had plenty of chances." It also delighted him the pre-match tactical talk went to plan. "I wanted the midfielders to hold the ball more and build the attack, rather than have sporadic attacks."
Upper Hutt aren't Miramar Rangers, the second-placed side in the Central League, but Hastings is now aware his side are improving and have the weapons to usurp the Wellington side.
"Absolutely they will (be a different proposition) but at least we can go there with a bit of confidence knowing that we can play and that we're capable of scoring goals.
"You know, for the last few games, we've created chances and not put them away but today we've created chances and scored four and we could have scored even more."
It's a big weekend coming up as the Park Island side will host Wainuiomata in a Chatham Cup encounter on the Queen's Birthday holiday.
Of the opportunities Hastings talked up, the clearest fell to Robertson with the scores level. He had an open goal but the ball had rebounded speedily off keeper Campbell and the captain hit it marginally wide.
It certainly wasn't one-way traffic and Upper Hutt almost got back to 2-2, Liam Higgins missing the goal by a few centimetres.
In Saturday's other matches, Miramar drew 1-1 at home against Wairarapa and Wellington United gained a much-needed 3-1 win at the expense of fellow strugglers Tawa.