[Yerma]

I think that when CO calls the river, he has at least a Jack. MP1's bet means he *may* have you beat. CO's call means that he has you beat here sometimes. Also, a 9 will almost never get slowplayed on the turn after you check because everyone will say "I can't expect anyone else to bet, so I will bet myself".

So if MP alone has you beat 1/4 of the time and CO alone has you beat 1/2 of the time and they each have you beat maybe 1/8th of the time, then you are beat approximately:
6/24 + 12/24 + 3/24 = 21/24th of the time. I think I may be overestimating how often CO alone has you beat, but not by much. So you are winning 3/24th or 1/8th of the time. Getting 8:1 pot odds, you have to be winning 1/9th of the time to make the call. So, you should call but there's not a lot of value here.