What do you mean by 'if not'

'Team A is one of the best teams in US, if not the best.'

Does this sentence mean 1) Team A is one of the best teams in US, in fact, perhaps they may be 'THE' best in US.

Or,

2) Team A is one of the best teams in US, though they may not be 'THE' best in US.

Please let me know, Thanks.