Alexander will deputise Dundee Utd's Paul Gallacher in Scotlands 8:00pm kick off against Canada from Easter Rd while James Collins has been named as a substitute for the U21's at Ninian Park as Wales take on Italy.
Both games are live on television tonight. Scotland's match is on Sky Sports 1 (channel 401). Kick off 8:00pm. Wales' U21 international from Ninian Park kicks off at 7:45pm and is being shown on BBC 2W (channel 102 for those in Wales and possibly 961 for those elsewhere).
It will be a debut for either player if they get a run out at some stage tonight.