It is early in the morning on the seventeenth day of the war. Karna goes to meet Duryodhana, 'Today I will fight with Arjuna and kill him, if not Arjuna will kill me. I was too pre-occupied yesterday and could not focus on Arjuna. You must also know that I am superior to Arjuna as an archer in my virtuosity, dexterity, swiftness, skill, defence, bravery, knowledge and courage. His bow Ghandiva is not equal to my bow. This bow was made by Vishwakarma specially for Indra. He gave it to Parusharama after destroying the Asuras and Parusharama used this bow and won twenty one expeditions on earth. And it is now with me.'
'I must also tell you where I lack when compared to Arjuna. He has a chariot gifted to him by Agni. His horses are indestructible. Moreover he has Krishna as his charioteer and his quiver is inexhaustible. These are not with me. If I had a charioteer like Shalya, who knows the heart of horses like Krishna does and a chariot with good horses, loaded with arrows, I am sure to defeat Arjuna as I am much superior to him.'
Duryodhana then goes to Shalya and bows to him and speaks very politely, 'I have come to you with a request which will help us in destroying the pandavas and it is for my benefit. Earlier, in the times of burning Tripura, Brahma was the charioteer for Rudra, in the same way, you can protect us by becoming the charioteer of Karna. If you take charge of Karna's chariot, he will defeat our enemies. Arjuna has Vasudeva as his charioteer, but Karna does not have one who is equal to Krishna. You are the only two remaining great warriors with us. Today Karna will fight Arjuna and he is confident of defeating Arjuna if you become his charioteer! If you both enter the battlefield together, like Aruna and Surya, the kaunteyas and panchalas will disappear like the darkness from the place.'
Shalya is shocked by this request, his eye brows come together in anger and his eyes turn red! 'Maharaja! It is not right to ask me to do this. How can I be a charioteer to a person of lower status! I am a crowned King and born to a family of Rajarshis. How can I be charioteer to a Sutaputra? You talk as if he is a better warrior than me, but I do not consider him even to equal to me. If you want, I will face the greatest warrior of our enemies or I will confront them all by myself. Only then will you know my ability. Asking me to be a charioteer to a suta is an insult. After such an insult, I do not want to fight anymore. I want to go back to my city, permit me to do so.'
Duryodhana stops Shalya with a show of respect and love, speaks to him softly and agrees with whatever he has to say. Then tells him, 'Karna or others, none is better than you. But Karna is better than Arjuna and you are better than Vasudeva, If Karna is better than Arjuna in his skills as an archer, you are better than Krishna in both, you are better than him with the horses and you are stronger!' Thus pacified, Shalya agrees to stay on. On one condition, 'I will speak anything that comes to my mind and no one should object to that. Duryodhana agrees.
Obviously Karna, unaware of the promise Shalya had made to Yudhisthira earlier, invites trouble on himself. I guess most of us have this type of experience. We get into trouble, in spite of some inner warnings, and blame luck!
Karna is surely a victim of fate as he is not even aware of the understanding between Yudhisthira and Shalya. That Shalya will try to demoralise Karna in case he is invited to take charge of Karna's chariot.