Rachel McAdams, Forest Whitaker and, specially, Jake Gyllenhaal show us how good of an actors they are. Also, we discover the great performance by Oona Laurence but that's the(one and only) big strength of the movie; its cast.
The story is the one told a thousand times without many new details that would make it any different. The directing is correct but the story is just too well known.
As far as boxing sport movies goes Southpaw isn't a film to remember, but the whole aspect of a criminal being made a successful man because of his wife/daughter, people in his life the MC deemed to fight for, added that one drama notch to get you all goose bumped.
Regardless, as far as boxing goes, these fights weren't doing it for me as a boxing sport fanatic and practitioner myself. They were unrealistic to a certain extend.