Cheltenham 2 Pompey 2
Pompey conceded a stoppage-time goal to draw 2-2 for the third successive away league game.
Patrick Agyemang opened the scoring with a cool early finish as the Blues dominated the opening stages.
But Jermaine McGlashan punished Pompey for their profligacy by equalising with the Robins’ first clear-cut chance.
Skipper Ertl gave the 1,560 travelling supporters plenty to cheer about, however, when he netted from close range late in the first half.
But it was not quite enough to secure victory as McGlashan poked home a late leveller.
Guy Whittingham made one change from the side that knocked Torquay out of the Johnstone’s Paint Trophy during the week.
Agyemang replaced Ryan Bird up front, while new arrival Shaun Cooper had to be content with a place on the bench.
Pompey started brightly, but Andy Barcham could only fire high over the crossbar following good work from Ertl and Danny East.
But the Blues were ahead on five minutes, with AGYEMANG taking advantage of some defensive dithering to collect Ricky Holmes’ pass and slide the ball past Robins keeper Scott Brown.
They might have had another moments later, but Holmes’ cross just eluded the advancing Jed Wallace at the far post.
Agyemang then let Cheltenham off the hook, blazing over from just a couple of yards out following some fine play down the right from Wallace and Yassin Moutaouakil.
Pompey were camped out in their opponents’ half, with the hosts struggling to deal with their slick passing play.
The Robins finally threatened on 28 minutes, but Sido Jombati’s cross flew straight into John Sullivan’s arms after taking a deflection off Joe Devera.
But the Blues were soon back on the attack and Brown had to come tearing off his line to stop Agyemang racing onto another incisive pass from Holmes.
The visitors were made to pay for not taking more of their chances, however, as Cheltenham equalised on 36 minutes.
Sullivan took too long to decide whether to come out and deal with Terry Gornell’s through ball, allowing McGlashan to latch onto it, round the keeper and slot home.
The equaliser gave the Robins a huge boost, with the stadium suddenly coming alive as the home support urged their side forward.
Mark Yates’ men were knocking the ball about with all the confidence that Pompey had shown earlier in the half.
But it was the Blues who went in ahead at the break – thanks to the most unlikely of goalscorers.
Wallace showed good determination down the right and sent in a low cross, that gave the unmarked ERTL the simplest of finishes from just a couple of yards out.
The skipper lashed the ball into the roof of the net and seemed in a state of shock until celebrating with what can only be described as some dodgy dad dancing.
Pompey came close to adding a third goal in stoppage-time, but Holmes saw his effort blocked after being teed-up by Agyemang.
Half Time: Cheltenham 1 Pompey 2
The Blues continued to pour forward at the start of the second half and Barcham’s acrobatic over-head effort flew narrowly over after Holmes’ free-kick had been headed back across goal by Ertl.
Then, when Brown could only parry Barcham’s shot, there were three players queuing up to score.
It was Wallace who went for it, but his scuffed strike was comfortably dealt with by the Robins back-line.
Holmes was next to go close, although it was unclear whether he was attempting to score directly from a corner that was just about pushed over by Brown.
Pompey had seen away leads disappear in their previous two away league games and were desperate for a third goal.
They were certainly creating plenty of openings and Barcham volleyed inches over on 63 minutes Holmes had headed the ball down.
But there were always going to be nerves while the lead was only one goal and it took a superb last-gasp challenge from Sonny Bradley to deny Gornell.
With Pompey visibly tiring, Whittingham made all three of his substitutions on 78 minutes.
Barcham, Holmes and Agyemang all took a deserved rest, with Cooper, Bird and Romain Padovani coming on.
It was backs to the wall stuff for the Blues in the closing stages as Cheltenham stepped up a gear in their hunt for a point.
But they suffered a heartbreaking blow deep into stoppage-time as McGlashan just beat East to the ball and poked it past Sullivan.
It might have got even worse for Pompey as there was still time for Gornell to find the net, although the Robins striker was denied by the linesman's flag.
Cheltenham: Brown (c); Lowe, Inniss (Penn 32), Elliott, Jombati; McGlashan, Noble, Richards, Deering (Harrison 66); Gillespie (Kotwica 57), Gornell
Goals: McGlashan 36, 90+2
Subs not used: Rivers, Taylor, Vincent
Pompey: Sullivan; Moutaouakil, Devera, Bradley, East; Wallace, Ertl (c), Ferry, Barcham (Cooper 78); Holmes (Bird 78); Agyemang (Padovani 78)
Goals: Agyemang 5, Ertl 44
Booked: East
Subs not used: Smith, N’Gala, Butler, Harris
Referee: Brendan Malone
Attendance: 4,776 (1,560 Pompey fans)