For example I checked several sports and betting sites for
K. Nishikori vs A. Dolgopolov
and
J. Tsonga vs D. Goffin
And other matches. The order of the players names is always the same at all sources so there must be a convention. I can't work out what the convention is though. It does not seem to be alphabetical or reverse alphabetical by first or last name and it does not seem to be by seeding/ranking.
I've never thought about this, but I'm pretty sure it's based on the draw. http://www.atpworldtour.com/en/scores/current/buenos-aires/506/draws In this case Nishikori is played above Dolgopolov, he is on the upper half whereas Dolgopolov is on the lower half, so Nishikori's name goes first. I checked WTA Dubai's draw for the week, and the name order for these seems based on the draw too, http://www.wtatennis.com/SEWTATour-Archive/posting/2017/718/MDS.pdf
I've never thought about this, but I'm pretty sure it's based on the draw. http://www.atpworldtour.com/en/scores/current/buenos-aires/506/drawsIn this case Nishikori is played above Dolgopolov, he is on the upper half whereas Dolgopolov is on the low