The Magpies were beaten 2-1 by West Ham United in Tuesday night's play-off final at St. James' Park, despite taking an early lead through Tom Heardman.
They were dominant for much of the opening period, but were pegged back on the stroke of half-time by Spanish forward Toni Martinez - who also netted against Rafa Benitez's first team for Oxford United in January.
Martinez completed the turnaround shortly after the break, with Beardsley honest in his assessment of the game from that point on.
"To be fair to West Ham, I thought they managed the game well in the second half, and when they scored the second goal, they were - in my opinion - the only team who were going to win," he told nufc.co.uk. "We maybe could have scored from a set-piece, but overall, their football was better than ours.
"The first half an hour, we played well. The second goal makes a massive difference, and if we don't get it - which we didn't - then they're still in the game. They score a goal that they're obviously happy with just before half-time, but if I'm being really critical, it was poor from us defensively.
"The three times we've played West Ham here, they have been really good games. I went into their dressing-room tonight and said exactly that. Fair play to West Ham - they are a good set of people, and they are a good football club. It's great for them - they have three London derbies in that top league, as well as the two Liverpool clubs and the two Manchesters. We'd have loved to have been in it - I'm not going to kid you - but we just go again and get ready for next season with a new crop. A few of those (tonight) will go out on loan, and then we will try and nurture the next set through."
Newcastle actually ended the regular campaign two places above West Ham, and also knocked Terry Westley's side out of the Premier League Cup.
The Magpies rarely strayed far from the promotion picture this term, and were unbeaten in the Premier League 2 between October and mid-January.
Meanwhile, Dan Barlaser, Yasin Ben El-Mhanni and Stuart Findlay were all handed their first-team bows by Benitez, with Curtis Good also returning to the fold after a lengthy absence.
And, despite last night's disappointment, Beardsley feels there is much to be positive about looking forward, and paid tribute to the players and backroom team alike.
"When you get to the stage we have, it is disappointing to lose - absolutely. But take nothing away from the players - they have had a brilliant season," he said. "We've used more than 50 players now - they've done us proud, and they've done themselves proud as well. For those that you'd say are a 'year older', they have to kick on, go out on loan, and hopefully get one step closer to the first team. Rafa was here tonight again, and he has supported us all season.
"We'll be in on Wednesday, sorting out who is going to stay and who is going to go - that's a job we have to do. Once we do that, the players will be ready to go and have their break. They've earned it - when you get your summer holiday, you should enjoy it. We work ten months of the year - and I'm not negative about that, because it's a brilliant job and a brilliant situation to be in - so they need to take advantage of it.
"It has been a brilliant season. The players have been outstanding, and what I would call the 'support group' - Ben (Dawson), Simon (Tweddle), Carl (Nelson), Haydn (Rockall), George (Ramshaw) and Chris (Terpcou) - deserve a lot of credit as well. They deserve as much credit as the players. Ultimately, though, that's what you're judged on - your players. And they have had a great season. Four have played in the FA Cup. It is what it is - we're trying to get them to the first team as quickly as possible."
