I'm with split-step and Eddy - call the ball out promptly or play it. That "second chance" issue should never come up. Either the ball was definitely out (and called as such right away) or it was in. Play on.
Even though a server or his/her partner might assume that their first ball was out, they shouldn't disregard the receiver's ruling. The only person that you should perhaps be apologizing to in that situation is your partner because you didn't effectively help with calling the serve.
The inclination to play a let may be well intentioned, but try to avoid that. Otherwise there's too much second guessing going on from across the net and it makes a mess of the integrity of the calls and the rhythm of the match. I've been there and given my marginal eyesight, I can be really generous with my calls sometimes. As soon as any of this assumption on my calls comes up, I like to immediately clarify that unless I call any ball out, it's in. That gives my opponents the heads-up to keep playing even if they see their ball land an inch or two out on my end.