The part of speech that is missing is the verb, without the verb, a sentence is incomplete. In this case, the sentence fragment "Manny Ramirez again" does not include a verb and does not have meaning on its own.
In order to change this sentence fragment into a complete sentence, a verb should be added. Examples:
"Manny Ramirez got sick again"
"Manny Ramirez was absent again"
"Manny Ramirez failed again"