However, a UEFA rule that allows a team to bring in a squad substitute if a player has been ill or injured for 60 days has allowed Spurs to make the change, but it can only be done up until the sixth game of the group phase, which falls this week with the game against Slavia Prague, which Tel can now play in.
You cannot normally change an association trained player for a non-locally trained player, but Spurs have been able to register the four required association trained players in Djed Spence, Archie Gray, Ben Davies and Brennan Johnson, which allows Solanke to move into the main group, so he can be replaced by Tel. The UEFA rule suggests that Solanke can come straight back in for Tel when he returns to fitness.
— Alasdair Gold, Football.London