Translation:The coach speaks with the goal-keeper in the second half of the game.
Another user explained this rule of the extra "a" article in another comment. I would post the link to that post, but I can't find the link. Here is what I copied into my Romanian "cheat sheet:"
Both Definiteness AND Adjacency required to avoid use of article al/ai/a/ale: In other words, the article is avoided when the possessed noun has both a definite article AND the possessed noun is placed right before the possessor.
If either of these two conditions is not met, then the possessive article appears:
o carte a copilului (lit. "a book of the child") (the possessed noun does not have a definite article); cartea frumoasă a copilului (lit. "the beautiful book of the child") (the possessed noun is not placed right before the possessor); o carte frumoasă a copilului (lit. "a beautiful book of the child") (the possessed noun does not have a definite article and is not placed right before the possessor).
My apologies for not linking to the original author of these examples as I did not save the link to his wonderful post.
I'm not entirely sure what the rule is. I think in this case it's because the noun determined ("repriza") has another attribute ("a doua") in addition to our genitive noun. Without that you wouldn't need the possessive article:
"Antrenorul vorbește cu portarul în repriza meciului" (doesn't make as much sense as a sentence, just illustrating the point).
You also need it when the noun is part of the predicate:
"Casa este a profesorului" ("The house belongs to the teacher"). In this case the predicate is "este a profesorului"
Compare that to the situation where "profesorului" is just an attribute of the subject:
"Casa profesorului este veche" ("The professor's house is old"). No article there.
"Antrenorul vorbește cu portarul în pauza meciului", now it makes sense (just to give a better example, because you said it didn't make sense - but it did, actually your sentence was quite ok, it is just our brain playing tricks with teh semantics, because we know the match has two rounds, but the sentence was perfectly right in romanian)
There is a second a. I specified the second a, because I did not understand its grammatical function within the sentence. When asking such a question, I try always to use a simple description of whether the item is in the word or sentence, so that the person who provides me with the answer can simply describe the grammatical function from a blank slate, as happened so helpfully here.
OK, I perhaps worded it a bit badly (probably through ignorance). Yes, in British football they are two separate jobs. But in Romanian Wikipedia, for example, Jürgen Klopp is given as "atrenor" of Liverpool FC. In British English he's "the manager", although it's true that he's helped by a team of coaches, probably what I was calling "trainers".
However, this course uses American English, where the equivalent of the British "manager" appears to be "head coach", or often, I think, just "coach". This would lead me to suspect that we could be talking about the main guy here, in AmE "(head) coach", in BrE "manager". So, talking specifically about football, I think the BrE variant, "manager", should also be accepted.