Steve Clarke said Scotland showed how good a team they are despite a late defeat in Spain, while John McGinn fumed at Scott McTominay's disallowed 'opener'.
Clarke saw his side's perfect run of five straight wins ended by late heartbreak in Seville, with Alvaro Morata and Oihan Sancet giving the hosts a 2-0 victory after McTominay's free-kick had been ruled out by VAR.
A draw would have been enough for the Tartan Army to secure their qualification for next year's European Championships, but they can still reach the finals should Spain pick up at least a point in their next qualifying game, away to third-placed Norway in Oslo on Sunday.
"We came here to show that we were a good team and I think tonight we showed that," Clarke said.
"Tonight was the first chance to qualify, maybe the result on Sunday night goes in our favour and we can qualify from that. But we don't qualify because of that result, we qualify because of the work we've done to have 15 points from six games.
"That's why we will qualify if a result goes our way over the weekend. If it doesn't go our way and Norway win, then we have a very realistic chance for the two games in November to win this section and that's what we'll focus on.
"We can be pleased with how we performed but the lads are really disappointed that we've lost the game because we didn't come here to lose.
"It's a VAR decision that goes against you, you just have to move on. At that stage in the game we were we're fine. The second goal puts a little bit of gloss on it for Spain, I'm not sure they deserved it as we have some good chances."
During the match, Clarke had urged his players to remain calm amid the controversy of McTominay's disallowed goal, which was overturned following a lengthy VAR review.
At the time, TV pictures said it had been ruled out for a foul by Jack Hendry on Unai Simon - but later replays showed he had been penalised for an offside, and had been found to have interfered with the Spain goalkeeper.
Speaking to Viaplay, vice-captain McGinn said: "He changed it in game, which was a frustrating thing. It shows it's not clear and obvious.
"At that moment, Jack makes a decision to step the other side. Is he going to save it? No chance, absolutely no chance.
"At first he says it's a foul, then he changes it to an offside when he realises it's not a foul.
"It's a hammer blow, that qualifies us that goal. They need to score two. I feel for big Scott [McTominay], but sometimes these things go for you and tonight it was never going to.
"We can't be too disappointed. We wanted to qualify tonight and we were capable of it. We don't want other teams to do it, we want to do it ourselves.
The big moments went against us. There's no doubt we can still improve but we put in some shift.
"We knew a point would get us there, and it's a really tough one to take with a sore blow losing Robbo so early.
"Then thinking we're ahead, that going against us, we regrouped but they scored the opener - maybe we can defend that better but it's a tough one to take.
"We competed for long spells, it's tough to win here but in the circumstances it was near-enough impossible.
"Everyone watching that game from a Scotland point of view, on the pitch, in the stand, in the dugout, it felt like we weren't going to get a decision.
"50-50 balls, going in for fair challenges and not getting them, it made it extremely difficult against a world-class team to get anything.
"You need a perfect performance to win here, and it was never going to happen."
Analysis: Were Scotland unlucky not to score?
Former Scotland international David Marshall on Sky Sports News:
"It is an unbelievable free kick into the top corner, but Hendry is standing half a yard offside and is interfering with the 'keeper unfortunately.
"That is a huge let-off for Spain, but it will give Scotland huge confidence.
"It is a foul, he affects Simon's positioning, he runs across him and makes a tiny bit of contact, but he affects the 'keeper and is standing in an offside position when it happens, so they cannot have any complaints, but it is very unfortunate.
"It has been an incredible effort, Spain dominated possession, had three or four clear-cut chances during the game.
"Scotland had a couple of chances, and the disallowed goal in the second half, but Spain are a top European side, especially in their back garden, it is a tough place for anyone to go.
"But Scotland are still in a good position to win the group, but a couple of lapses of concentration and an unlucky slip by Hickey cost them the second goal.
"It was always going to be a tough night, but they equipped themselves well, dug in, managed to get themselves through the first half, but that domination of possession that Spain had eventually told in the end.
"Everybody would have snapped your hand of for the position they are currently in, it would have been great to get to Germany tonight, but I've no doubt Scotland will be there, whether it be this weekend, or next month.
"Steve has built a great squad, with great belief to come here and defend really well and they were unfortunate not to take the lead tonight and it would have been interesting to see how the game would have gone then.
"Plenty of positives though and let's see how Spain and Norway get on at the weekend..."
McKenna: Disallowed goal gave them lift
Scotland defender Scott McKenna on Viaplay:
"It's disappointing, when we score that goal I don't think there was too much in it for it to be disallowed. If that stays as a goal, it changes the game massively in our favour.
"We quietened their crowd, and disallowing the goal gave them a lift and let them come back to it.
"Aaron [Hickey] has been brilliant since he's come in for us, it's unfortunate. [Ryan] Porteous just about bails him out but the clearance hits their man and goes in.
"It's still in our hands to top the group, there's a couple of games next month and if we win them we'll do that.
"Obviously there's a game this weekend between Spain and Norway which could go in our favour too, so there's still plenty to look forward to.