I've never heard the term sidelined used in that manner, it must be an American thing.
This is from the BBC website about two of today's matches.
Quote:Arsenal are set to name a weakened team for their Europa League tie against BATE Borisov on Thursday.
Laurent Koscielny, Mesut Ozil and Alexis Sanchez are among the players unlikely to play in Belarus.
Summer signings Alexandre Lacazette and Sead Kolasinac are also not expected to feature.
Danny Welbeck will miss out through injury as Arsenal look to build on the 3-1 victory from their European opener against Cologne.
Quote:Defenders Phil Jagielka and Michael Keane will miss Everton's Europa League group game with Apollon Limassol at Goodison Park because of injury.
Captain Jagielka has a hamstring problem while Keane has a cut foot.
If I've understood RP correctly he's saying that if a player is injured before the match and will have to miss out he is sidelined. However if he is injured during the match he's substituted for another player.
Substituted is used in the same way in the UK.
My spell check doesn't even like me using the word sidelined btw, it's got a big red squiggly line underneath it