Tranmere's second long distance trip in a week ended in a 2-0 away defeat at Gillingham.
A second half goal from Bradley Dack put the home side ahead and Cody McDonald sealed the points with a late breakaway attack as Rovers threw everyone forward in search of an equaliser.
The result left Tranmere two points and two places above the bottom four.
There were two changes to the Tranmere team that had started three days earlier at Crawley as Ryan Lowe and Jason Koumas returned from injury to take the place of Jake Kirby and the injured Steve Jennings.
The home side started strongly and forced Tranmere back into their own area early on, with Matthew Pennington having to block a shot from Charlie Lee and Liam Ridehalgh and Ian Goodison heading clear.
The frantic pace continued at both ends, with Jean-Louis Akpa Akpro flicking goalwards on six minutes while Lee send a diving header wide at the back post from Adam Barrett's cross.
Goodison tracked back well to prevent Cody McDonald from a shot at the near post on eight minutes after initially losing his man and Cassidy side footed wide from the penalty spot two minutes later after being found by Lowe.
Owain Fon Williams saved from McDonald at his back post on 19 minutes and, after Cassidy brought down a pass from Koumas and saw his shot deflect away from goal, Goodison produced another timely block to keep Lee's effort away from goal.
Akpa Akpro, now in a more central role after a switch to 3-5-2, fired into the side netting from 25 yards on 27 minutes, a minute before injury forced Goodison to be replaced by Danny Holmes, with Matthew Pennington moving into a more central position.
Fon Williams did well to tip Akinfenwa's powerful header over the bar at a Gills free kick on 40 minutes and the keeper was lobbed by the striker on the stroke of half time but Akinfenwa's effort went past the post.
A 25 yard drive from Power was charged down following a good spell from Rovers ten minutes into the second half, while Fon Williams did well to save McDonald's low strike with his feet soon after.
Long range efforts from Koumas and Akpa Akpro were well saved by Stuart Nelson while Cassidy saw a back post effort blocked after a superb run down the right wing from Ash Taylor on 68 minutes.
Cassidy powered through the Gills half on 69 minutes and held off two defenders but his well struck 25 yard shot went inches past the left hand post.
Fon Williams saved from McDonald at his near post on 72 minutes and held a header from the striker soon after.
On 78 minutes the Gills took the lead. The ball was crossed in from the left by Joe Martin and Bradley Dack unleashed a ferocious volley from 12 yards which went straight past Fon Williams and into the top left corner.
Cole Stockton replaced Koumas with five minutes of normal time remaining and the striker had a 20 yard shot deflect just past the post and wrong footed keeper Nelson in added time. However, from the resulting corner, Tranmere had all 11 men forward and a counter attack allowed McDonald to race forward, hold off Pennington and shoot into an empty net from 35 yards.
Gillingham: Nelson, Hewitt, Barrett, Legge, Martin, Gregory, Lee (Dack 66), Weston, Hessenthaler, Akinfenwa (Kedwell 70), McDonald. Unused substitutes: Baxter, Linganzi, Whelpdale, Harriman, Fagan.
Tranmere: Fon Williams, Pennington, Taylor, Goodison (Holmes 28), Ridehalgh, Brown, Power, Koumas (Stockton 85), Akpa Akpro, Lowe, Cassidy. Unused substitutes: Mooney, Boland, Arthurworrey, Kirby, Rowe.
Referee: Michael Naylor
Yellow cards: Martin (35), Hessenthaler (52)