The first sage evaluated Soverick before the competition but didn't think him overly skillful compared to the others. Soverick has a powerful soul for a king of law but his level of skill wasn't estimated to be high because he rarely fought.
The erroneous estimate of his strength has changed in light of recent events. But before that fight with the dragon, the first sage only thought that Soverick had a shot at being concerned about the title of sage. There are a lot of others who also have a shot at becoming sages too.