Less we forget, Barcelona have IMO the best DM in the world at cb so he's for sure not irreplaceable, however he suits Barcelona's system very well for keeping the ball & doing the simple things. 100m isn't realistic anyways, it'd be more round the 30 mark if there was an offer, i wouldn't let him go that easily though.
Mascherano was great at Liverpool, not so much with us because his duties were simply breaking up play and being an enforcer as Pool play very differently from us; he himself admitted that. Sergi is the best in the world for BARCA and would probably flop at some other clubs because of his style.
That's why I was slightly annoyed when we bought Mascherano and then Song, and almost fell out of my chair when I saw Mascherano's buy-out clause in July. Neither of them would ever usurp Sergi unless he had a poor run of form or major injury, but it's still not worth keeping a great (and very expensive) player on the bench in the event our CB's are healthy. Song has some ability to move forward like Yaya Toure did but obviously isn't as skilled. But with Jordi Alba we have another skilled and fast player moving forward with Alves.
With the state our backline is in, I hope we avoid pushing too many men forward