The Tigers took the lead just four minutes into the game. A well-worked move down the right-hand side allowed George Honeyman to slide in Smallwood, whose first time shot slipped desperately under Simon Moore.
It would not be long before they extended their lead either. The Sky Blues failed to properly clear a Honeyman corner, and Longman fired the loose ball in off the crossbar to double his side's advantage just before the half-hour mark.
Sky Blues' defensive woes strike again
Smallwood's opening goal is the 23rd time that Coventry have conceded the first goal this season.
For all the attacking quality and flair Mark Robins' side has displayed this season, there can be no doubt that they have let themselves down defensively.
And that was on display for the 15,000-strong crowd in attendance on Wednesday night.
Missing captain Kyle McFadzean, the Coventry back three looked shaky for large parts of the game, both in and out of possession.
Hull's opener came from a rushed clearance from Jake Clarke-Salter which allowed the away side to pile the early pressure on and make the breakthrough.
As for the set piece that led to the second, it was a case of rinse and repeat for a Coventry side which has looked underwhelming both attacking and defending set-pieces all season.
Plenty for Hull to shout about
Not that Hull needed to be particularly on their game on Wednesday night, but they still impressed.
Whilst they might not take the game to teams with the bold style that their opponents can when it is their day, their solidity and threat on the counter-attack certainly should not be downplayed.
Defensively, they closed off the middle of the pitch to great effect, packing the midfield tightly and leaving no pockets of space between the back line and midfield.
When going forward, Shota Arveladze's side were certainly effective if not brilliant.
It was not a pretty watch, but Tom Eaves posed a physical threat that the Sky Blues struggled to deal with all night.
What Eaves offered in aerial danger, Lewis-Potter offered with skill and technical quality, and the two almost combined to give Hull a third just after half-time when Eaves forced Moore into a near-post save.
Again, whilst Arveladze's side are not the easiest on the eye, there is definitely plenty to build on as Hull look to climb the table under new owner Acun Ilicali.
Inconsistency will kill Coventry's play-off hopes
Whilst they have no doubt exceeded expectations this season and provided great entertainment for both supporters and neutrals, there can be no doubt that inconsistency has plagued the Sky Blues this season.
Robins' men have not strung together an unbeaten run longer than two matches since November 2021, and even then three of the four game they went without loss were draws.
The Midlands side's struggle for consistency are epitomised by the performances of Callum O'Hare in the 4-1 win over Sheffield United and the frustrated figure he cut during the loss to Hull.
Against the Blades, O'Hare was a nuisance for the away side's defence. Out of possession, he was constantly closing down, applying pressure and making the defenders' lives difficult.
And when he had the ball, he was constantly causing problems, manoeuvring in tight areas, sliding passes in and around the box and providing a goal threat - scoring twice and assisting Matty Godden.
However, against Hull, it was a completely different story. The early goal saw the Tigers sit in a compact shape and shut off all the space around their box.
O'Hare struggled to create anything and became increasingly frustrated as the game wore on.
The mazy runs and the clever passes he was able to make against Sheffield United were not coming off for him nor the Sky Blues in general.
It resulted in a bad performance and result on the night and it is a story that is seemingly going to cost Coventry their place in the Championship play-offs.