The Honda factory rider returned to MotoGP action at Assen after withdrawing from the last round at the Sachsenring following five crashes during the weekend that left him with multiple fractures.
Marquez crashed into Enea Bastianini during Q1 in an incident he later apologised for, and was unable to progress from his 17th position on the grid in Saturday's sprint race.
The result represented the lowest ever on-the-road finishing position for the eight-time world champion, who also suffered a crash in Friday's FP2 session, in his MotoGP career to date.
He languished almost 20 seconds behind sprint winner Marco Bezzecchi's VR46 Ducati after just 13 laps, having taken a soft front tyre to gain maximum feedback, and later explained that he was "too relaxed, not pushing".
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Reflecting on his struggles, Marquez said only the long layoff following his arm injury sustained at Jerez in 2020 could surpass his current experience.
"Apart from the [2020] injuries, this is the worst moment of my sporting career," he said.
"But defeat is the easy option. And I will never choose the easy way.
"Right now I'm riding for myself; for my engineers. Going half a second a lap slower, the problems are the same."
He added: "Today I saw that I wasn't in my place."
Source: Autosport