Sunderland and Luton shared the points in a 1-1 draw at the Stadium of Light in League One as both teams ended the match with 10 men.
Victory for the Black Cats would have seen them leapfrog their opponents and move up to second place in the table and they made the perfect start when Chris Maguire scored after 16 minutes.
Luton, who lost their manager Nathan Jones this week to Stoke, levelled in the 67th minute through James Collins' penalty but after getting back in the game, Danny Hylton was then sent off three minutes later.
Sunderland were unable to make their numerical advantage count and Maguire also received a red card in injury time.
It meant Pompey's lead at the top of the table was trimmed to just four points, despite Kenny Jackett’s men losing 1-0 at home against Blackpool.
Charlton and Barnsley were able to narrow the gap to the automatic promotion places as both recorded comfortable 3-0 wins.
Lyle Taylor, Darren Pratley and Karlan Ahearne-Grant, from the penalty spot, were on target in the Addicks' success at Shrewsbury.
The Tykes defeated Yorkshire rivals Bradford at Oakwell courtesy of goals from Jacob Brown, Kieffer Moore and Alex Mowatt.
Lee Tomlin celebrated his 30th birthday with a goal as he set Peterborough on their way to a 2-1 victory against Rochdale on his return to the club.
George Cooper also scored for Posh before Ethan Hamilton's last-minute reply for the visitors.
Peterborough's win saw them move back into the play-off places at the expense of Doncaster, who conceded late goals to lose 3-2 at Wycombe.
Rovers were in control after strikes from John Marquis and Tommy Rowe but Paris Cowan-Hall reduced the Chairboys' arrears after 77 minutes.
Curtis Thompson equalised for Wycombe in the final minute before Cowan-Hall headed the winner deep into injury time.
Plymouth were the only team in the bottom four to win on Saturday as they prevailed 3-2 at Southend.
Antoni Sarcevic, Freddie Ladapo and Ruben Lameiras gave Argyle a three-goal lead but Simon Cox, from the penalty spot, and Charlie Kelman netted late replies for the hosts.
AFC Wimbledon stay bottom of the table after drawing 1-1 at Coventry.
Former Pompey player Jake Jervis gave the Dons an early lead but Luke Thomas levelled things up in the second half.
Second-half goals from James Henry and Jamie Mackie saw Oxford battle back for a 2-2 draw at Fleetwood, who had led after first-half strikes from Wes Burns and Paddy Madden.
Bristol Rovers extended their unbeaten league run to five games with a goalless draw at Accrington while Scunthorpe made it four wins on the bounce with a 2-1 victory at Walsall.
Lee Novak netted the winner after Nicky Devlin had cancelled out Funso Ojo's opener for the Iron.
A bad week for Burton got worse with a 3-2 home loss to Gillingham.
Elliott List’s goal and a Callum Reilly penalty gave the Gills the half-time advantage but Scott Fraser’s double had the Brewers, beaten 9-0 by Manchester City in the Carabao Cup semi-finals, level again by the hour mark.
However, Josh Rees broke Burton hearts with the decisive strike in injury time to give Gillingham the three points.