The eight-time world champion fractured the first metacarpal of the thumb in his right hand in a controversial collision with Miguel Oliveira during the Portuguese Grand Prix season-opener last month.
Following immediate surgery to stabilise the fracture, the Honda rider has been sidelined and will miss this weekend's Spanish GP at Jerez.
After scans on Tuesday, Marquez was told it was "too risky" to return to action four weeks into what doctors initially told him was a six to eight-week rehabilitation period.
Asked if was playing it safe to avoid the risk of a crash, given the injury woes he has already suffered since 2020, Marquez said: "If I'm competing it's because I want to take the risk. And I tried my 100% to come here and to ride here.
"But when three medical teams say that you are doing a crazy thing and if you ride you will damage again, then you must accept.
"But the main risk was not crashing: it was the pressure on the handlebar, I will damage again.
"Especially because it's a very small crack, but it's a crack that gives the stability to the finger.
"And this finger is one of the most important ones, especially on the braking point.
"I broke that bone in that kind of situation: it was an impact and that kind of situation I will repeat every brake point.
"So, the problem is if I injure it again, they tell me it would be big damage, not only for three months more but also for my career because now they were able to fix it in a very good way.
Source: Autosport