the font is memorably found at almost all of nike-sponsored club on their back of the shirt

Vador  Suggeriti da xulo777 

In other teams using this, it seems that this is a modification

nope, they're all same
barca, inter, aston villa, porto, juventus, celtic, (probably more than these) use the font.

http://www.soccerbible.com/cfs-filesystemfile.ashx/__key/CommunityServer.Blogs.Components.WeblogFiles/football-shirts.2011.July.Celtic+Away+11+12/Celtic_2D00_Away_2D00_Updated_2D00_Tech1.jpg

http://www.soccerbible.com/cfs-filesystemfile.ashx/__key/CommunityServer.Blogs.Components.WeblogFiles/football-shirts.portugal.Porto_5F00_1112/Porto_5F00_1112_5F00_details.jpg

http://www.soccerbible.com/cfs-filesystemfile.ashx/__key/CommunityServer.Blogs.Components.WeblogFiles/football-shirts.Juventus.Juve_5F00_Hm_5F00_1112/Juve_5F00_Hm1112_5F00_juve.jpg