Pace is not the most important factor in being a good centre half. Mertesacker is currently far better than Jones, who can't even make it into United's centre of defence! It doesn't matter who wanted who, the point is Mertesacker is currently better than Jones is.
Talking in cliches again... It's not, clearly. Most of the best defenders in the league aren't particularly quick.
Well clearly they wouldn't or the top central defenders would all be able to do the 100m in 11 seconds. Positioning, leadership, bravery etc. are more common traits in top defenders.
Does he even sprint in that video? No one doubts he is quicker than Mertesacker. Everyone but you and Phil Jones' mum still knows Mertesacker is a better footballer.