McLaren driver Lando Norris took his maiden grand prix win after he benefitted from the safety-car period following a crash between Haas' Kevin Magnussen and Logan Sargeant in the Williams on lap 28 of the race.
Norris was the last of the frontrunners to pit, and managed to do so under safety-car conditions, meaning he emerged ahead of Max Verstappen to keep the lead.
Sainz was running in front of Norris but had pitted a lap earlier, under race conditions, dropping to fifth by the time the accident occurred.
Had Ferrari waited another lap, Sainz feels he would have emerged in the lead with a shot at winning the race.
"Frustrated, because we were ahead of him before that pitstop before the safety car," said Sainz of his race.
"If we would have extended one more lap, we would've caught the safety car and we could have won the race too."
Ferrari team principal Fred Vasseur acknowledged the poor timing of the safety car, and joked that he "forgot the crystal ball".
He said: "I was not aware that Sargeant and Magnussen would crash the lap after! Of course, when you are in this situation, you are a bit unlucky – or I would say probably that Lando was a bit lucky, because he was the only one on track.
"But more than this, I think it's the fact that they put the safety car in front of Verstappen. They're so used to have Verstappen leading the pack that they send the safety car in front of him!
"The safety car was quite slow, and it was a very good move at the end for Lando."
Sainz went on to finish fourth on track but was demoted to fifth by a penalty for his clash with Norris' team-mate Oscar Piastri.
The duo made contact as Sainz dived down the inside of Turn 17 on lap 39, the Spaniard seemingly losing the rear of his car and hitting the front of the McLaren.
Although Piastri fought back over the next corners, the Australian went off track at the end of the start/finish straight and had to concede his position.
Sainz was handed a five-second penalty after the race, dropping behind Piastri in the final results.
The Ferrari driver said he had to resort to an aggressive dive because he could not match the top speed of the McLaren on the straights.
"I realised it was time to be aggressive because everyone was being aggressive today," Sainz said before his penalty was announced. "And if I needed to get a move on Oscar, you could see that we were struggling on the straights, this meant that I needed to send one down the inside. I did it.
"And good pace towards the end, catching the guys in front, Max and Charles, but it was too late. I lost much time with Oscar."
