Translation:He is a main player on our team.
I wrote "group" but it was not accepted. I think group suits here as well as ομάδα surely means group.
"a main player" sounds not quite right in English - we'd perhaps say "a key player", or translating a bit more freely, "one of the main players".
Just a thought, in English it would probably "on our team" instead of "in our team" :)
"in" is more normal than "on" here in British English. I think the reverse is probably true in American English.
Βασικός = basic. In Greek it seems to have a broader meaning than "main" in English. Principle, essential, lead, core, elemental.
'Ενας βασικός παίκτης' means 'A basic player'. However the phrase 'a key player' gives the right nuance in English.
Key+noun (in English)=noun+(-κλειδί) (in Greek): Key player=Παίκτης-κλειδί.
I had 'primary' player, which was marked wrong. But surely 'primary' means 'main'.
I wrote "star", but I guess the meaning is "first team". The problem is that in most sports each position has a name, and each position is important, so they're all "main" players unless they sit on the bench. Maybe if he plays in an important position (e.g. pitcher) he's a "main" player?