Xavier expected none of this.
In his opinion, eliminating Sarah would only increase their chances of victory.
Of course, it's not entirely true.
Even though their team strengths were equal, he was undoubtedly the least injured and hence, the strongest.
If they followed his plan and faced off Sarah together, then firstly, William and Philia would be eliminated.
At the same time as them, Sarah would be also be eliminate.
Once that happens, he'd immediately attack Maissa and let Rodey eliminate her.
Then there'd only be Ashtarh and Tiama vs Rodey and Him.
He had been saving up his strength for this final fight.
Given the state of Ashtarh and Tiama's injuries, he was confident to help Rodey beat Tiama and he himself could beat Ashtarh.
Finally, it'd only be Rodey and him.
But that only meant he'd win.
A perfect plan.
The best map to his victory.
Alas.