Leyton Orient boss Russell Slade admits it was "very disappointing" Peterborough's goal was not disallowed for offside after their 1-1 draw in the League One play-off first leg.
The Posh opened the scoring through Britt Assombalonga's first-half header but the striker appeared to be in an offside position when he put the ball in the net.
Slade said: "Clearly Assombalonga has got the last touch in an offside position. For that not to be seen is very disappointing."
Orient responded strongly and were well worthy of their second-half equaliser through Moses Odubajo.
Slade said: "Full credit to my team. We kept grinding away in the second half, we were dominant in patches and created chances all afternoon. Thankfully we got one in the end.
"That's what I said to them at half-time. We didn't have to go looking for any magical recipe to get ourselves back in the game. It's the values we talk about like never giving up and the work ethic, character, togetherness and that desire.
"All those qualities and values we've had all season we needed to show in the second half and we did that in abundance and I was proud of them. On another day on a better pitch maybe the game might have got away from Peterborough."
Slade spoke to his players in a group huddle on the pitch following the draw where he reiterated the job was far from complete ahead of Tuesday's second leg at Brisbane Road.
The O's boss said: "There's still a lot of work to do because that's what I'm like. There's still an awful lot to do. We've got a result and it's level but there's still so much more to play for.
"It's not a time for celebration. It's a time for digging in and recovering now which is what we're going to do and get ready for Tuesday."