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.
"But if I re-injure that, maybe it could be the end of my career because it's a very important finger.
"So, for that reason, it was an easy decision. When three medical teams say to you that you will get injured again if you ride, it's an easy decision even if you are 30-years-old, 20, or if you are 15. You cannot be against the doctors. They are the professional ones."
Had Marquez been able to ride this weekend at Jerez, he would not know whether or not he would have to serve the double long lap penalty he was issued for the Oliveira crash in Portugal.
After the FIM stewards altered the wording of its penalty notice to say Marquez would have to serve it at the next round he was able to compete in, rather than in Argentina as was initially stated, Honda lodged an appeal.
The FIM stewards referred the case to the FIM Court of Appeals, which granted a stay of execution on the penalty until a resolution is finalised.
Commenting on the situation, Marquez said: "Honestly speaking, and believe me I don't follow a lot that situation.
"Of course, I received a penalty on Sunday in Portugal that I was completely agreeing with.
"But then I don't know why they changed it after two days. Then the team decided to appeal, but as you can imagine that when you are injured you don't think about these things, especially when the doctors say to you it will be around six, eight weeks.
"Believe me, the worst penalty for a rider is being injured, losing three races.
"The team continues with the appeal because normally when you receive the penalty, when you agree, you sign the paper and it must be that penalty – not another one."
Marquez hopes to be able to return to action at the French Grand Prix next month, but concedes "this is not 100% assured".
