"I'm so shocked and saddened by the loss of Marco. When things like this happen it reminds you how precious life is, it makes me feel sick inside. All I can say is how sorry I am for Marco's whole family I can't imagine what they are all going through and our thoughts and wishes are with them at this time. I hope they all stay close and pull through this tragedy together."
"In a tragedy like this there is not much to say. I just want to give my condolences to his family and all the people who love him. I've been with his father and all we could do was to hug, nothing else matters. It was a fatal accident and everybody in the paddock remains in shock. Many times we ourselves forget how dangerous this sport can be and when you lose people on the way nothing has any meaning. It's clear that we all do what we like, what we love, but on days like today nothing matters".
"In these circumstances, words don't seem to be appropriate. I think of Marco's family and all the people dear to him, in particular his father and mother. I also have a child and what happened today is the hardest situation you can imagine. I watched the images and I'm shocked: in a race you fight and push hard and disaster is often around the corner. Marco was a strong rider and he always pushed hard. We raced together since we were kids, I saw him always pushing to the maximum, he crashed many times, but without major injuries, he was seemed invincible. What happened today seems impossible".
"Sometimes life just don't make sense... RIP #58 your were a star on & off track we all going to miss you."
"Super Sic rest easy..."
"RIP Marco Simoncelli! A great rider and all round nice guy. My thoughts are with all his family & friends. I will never forget today... #58"
"I am in shock. We are bike riders and we are aware that there are risks involved with what we do, but we also know that every day our safety is looked after more and more by the organisers. These past few years have seen a huge amount of work done to try and make our job even safer.
"Despite this, there are moments in which misfortune can lead to tragedy -and we saw this happen today with Marco Simoncelli. Today is another tough day for motorcycle racing. We have lost a great companion, and I will remember Marco as a great rival with whom I had some fantastic battles in the past."
"The Cardion AB Motoracing team extends its deepest condolences to the family, friends, and colleagues of Marco Simoncelli, who succumbed to injuries he received in the race at the Sepang International Circuit."
"I don't know what to say... Only that you will be missed. Rest in peace Marco."
"God Speed #58 Simoncelli... Your fighting spirit will live on forever!"
"R.I.P Marco A special talent that will be missed... Thinking of your loved ones, and all the motogp paddock..mark"
"R.I.P Marco... Such an exciting talent lost. My thoughts are with his family, friends and everyone involved in MotoGP. Sometimes Motorsport can be so cruel..."
"RIP Marco Simoncelli. My thoughts are with his family, friends and team at this extremely sad time. Another tragic loss at such an early age."
"Rest in peace Marco Simoncelli! A true inspiration, amazing rider and gentleman! Your legacy will never be forgotten!"