Pompey’s chances of being crowned League Two champions were given a significant blow.
Leaders Doncaster enhanced their title credentials with a 4-1 win at stricken Leyton Orient.
Rovers remain six points clear of Plymouth at the top of the table but Donny were made to work hard by the division’s bottom side.
Tommy Rowe put Doncaster ahead with a low effort on 36 minutes but Tom Parkes smashed in an equaliser before the break.
However, ex-Blues man John Marquis grabbed a brace after the interval and Mathieu Baudry added a late fourth.
Plymouth kept tabs on the leaders with a 1-0 win over Morecambe and went seven points clear of Pompey in second.
Graham Carey curled home the only goal of the game from outside the area after 17 minutes.
Despite Stevenage moving within four points of the Blues in fourth, Paul Cook’s side were fortunate that their other main automatic promotion rivals dropped points.
Carlisle drew a blank for a fifth successive game as their top-three hopes faded further with a 2-0 defeat against Mansfield.
Second-half efforts from Matt Green and Shaq Coulthirst left Carlisle with one point from five games and they have now failed to score in over 500 minutes.
Luton also failed to close the gap on the automatic spots as they were held to a 1-1 draw at home by Exeter.
Danny Hylton cancelled out Jake Taylor’s opener for the Grecians, who remain in the top seven.
Blackpool are just a point outside the play-off places after a 3-1 win at struggling Newport.
Bright Osayi-Samuel fired in off the bar after 16 minutes and Mark Cullen converted a second-half penalty after Osayi-Samuel was clipped in the box.
Alex Samuel pulled one back for Newport but defeat leaves them seven points adrift of safety, with Osayi-Samuel grabbing a late third on the break.
Cheltenham slumped to a 1-0 defeat at home to Cambridge in the week manager Gary Johnson underwent heart surgery.
Medy Elito grabbed the only goal of the game after just two minutes of play.
Wycombe closed the gap on the play-off places with a 2-0 victory at Hartlepool.
Adebayo Akinfenwa netted his 17th of the season to give the Chairboys a first-half lead and Paris Cowan-Hall made the points safe in stoppage time.
A Chris Dagnall brace gave Crewe a 2-0 win over Colchester
Grimsby were held to a 1-1 draw by Crawley. Dan Jones put the Mariners ahead but Rhys Murphy equalised and the hosts had to see the game out with 10 men after Danny Collins was sent off late on.
Accrington picked up a 1-1 draw at Yeovil despite Scott Brown receiving a straight red card after only 22 minutes.
Omar Beckles gave Stanley an unlikely lead before half-time, but Yeovil’s pressure eventually told when Francois Zoko netted after 74 minutes.
On Sunday, Notts County beat Barnet 1-0 despite playing most of the game with 10-men.
Mark Yeates was given a straight red card after just 11 minutes for a foul on Ricardo Almeida Santos, but Matt Tootle’s second-half strike was enough to seal the win.