The tennis player was not ? as the best player until he won the championship.
The tennis player was not considered the best player until he won the championship.
When Ada Lovelace was alive, women were not ? as mathematicians.
When Ada Lovelace was alive, women were not recognized as mathematicians.
The tennis player was not considered the best player until he won the championship.
To find the missing word in the sentence, we need to understand the sentence structure and context. The phrase "not ? as the best player" indicates that a word is missing which would complete the sentence.
Based on the context provided, it seems that the missing word should describe the tennis player's status before winning the championship. One possible word that fits this context is "recognized."
So, the completed sentence would be:
"The tennis player was not recognized as the best player until he won the championship."