The head coach’s verdict came after a 2-0 defeat at Derby County exposed a familiar weakness.
The Swans were beaten by second-half goals from Rhian Brewster and Patrick Agyemang, both stemming from Callum Elder corners, as Derby capitalised on dead-ball situations to secure the points.
The result leaves Swansea six points adrift of the top six – with Derby now occupying that final play-off berth – and sitting 16th in the table, 10 points above the drop zone.
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For Matos, the manner of the loss was as frustrating as the outcome. Swansea had controlled much of the first half at Pride Park, pressing aggressively and dictating possession, only to unravel when Derby turned to their aerial threat.
“In the Championship, set-pieces are really massive. We knew that – we are using them as well at the moment,” Matos said.
“Derby scored from a set-piece and that changed a little bit the game.
“First half I thought we were really good, especially the way we control, aggression, counter-pressing was brilliant. We got some situations where we can be effective and they are what we need to grab.
“Then it's about how can we react to a set-piece goal. We made some steps to get back [into the game], then the second goal was tough for us.
“It's important that we grab the good things and keep improving the other ones. Today was clear that we have to keep improving set-pieces.”
Despite suffering a 10th away league defeat of the campaign – and only their second loss in six matches – Matos remained encouraged by his side’s broader progress.
“I think at the moment the way my team and my players are performing, I am really proud of them,” he said.
“They are buying into ideas, they are putting in a lot of effort to improve. We are all improving.
“Today was about set-pieces. We suffered from that and that's what we need to keep focused on for the next games.
“If we look at some away performances, the performance is there but the points are not.
“At home we are getting the points, but we rely on training, not the past.”
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Swansea’s home form under Matos has been a source of optimism, and they now return to the Swansea.com Stadium for fixtures against Bristol City next weekend and Preston North End the following Tuesday.
Those upcoming matches will come without Marko Stamenic, who is suspended after collecting his 10th booking of the season for a foul on Agyemang at Derby.
The New Zealand midfielder’s absence could open the door for Jay Fulton, fresh from signing a new contract, to anchor the midfield.
Derby head coach John Eustace acknowledged his side had been second best for long spells before the interval but felt tactical tweaks and a focus on set-pieces proved decisive.
"First half the gaps between front and back were too big which was disappointing,” said Eustace.
“Every time we won the ball back, we lost a duel or were a little slower in possession which gave them the emphasis of the game.
"But they didn't rally cause us any issues. Second half we changed one or two things and our shape was much more connected.
"We spoke about how we'd look to beat them on set-pieces and today was very much a set-piece game.
"We haven't won at home consistently enough this year and the main thing was to make sure we won the game."
For Swansea, the path towards the play-offs remains open but narrowing. Matos believes the foundations are in place — yet if they are to close the gap on the top six, he knows improvement at both ends of the pitch, particularly from corners and free-kicks, is non-negotiable.
