Due to injury and recovery, De Jong missed last year's EUROs, and five of the Netherlands' six Nations League group stage matches. His 73 minutes against Spain were the most minutes De Jong had made for the Netherlands since the 2023 UEFA Nations League finals.
"I do feel like I'm back - for a while now" De Jong told the NOS. The midfielder was a question mark before Thursday's game after missing last weekend's LaLiga game against Atletico Madrid due to illness.
"I still need to get a bit fitter though, because I was really empty at one point. Quite quickly already, so that surprised me too. Maybe it's a one-off because at Barcelona it's not too bad. It could be to do with being ill."
The Netherlands ended up drawing 2-2 to Spain after Mikel Merino bagged an injury-time equaliser. Spain's opener came after Ajax defender Jorrel Hato wastefully lost the ball to Lamine Yamal.
Former Ajax midfielder De Jong still saw his 18-year-old teammate play a good game, even keeping Yamal to zero successful dribbles. "Mistakes can be made, and I think Hato played a very good game. Impressive, after that first goal, but I think he played very well," said De Jong.
"Making mistakes is possible, then you just have to keep going. Keep showing guts and play with confidence. He has done that, and that is very clever when you are so young."