Gawd, it must be humiliating to try to be grammatically correct to the point of sounding pretentious, only to find out you’ve committed a grammatical goof. You silly goose! The tennis player could feel badly if he had oven mitts on his hands.
The good editors who work on the Yahoo! front page could use a little lesson on linking verbs. Those are verbs that express emotion or a state of being, and not an action. Some verbs like feel and smell can function as either a linking verb or an action verb. You don’t use an adverb (like badly) to modify a verb like feel when it’s used as a linking verb.