Sam Johnstone's smile beamed like the McDiarmid Park floodlights after the goalkeeper's accomplished Celtic debut. Making his first league appearance in 21 months, the Wolves loanee impressed as Celtic preserved their 100% start with a hard-fought 1-0 win at St Johnstone. Johnstone was something of a surprise inclusion in place of Viljami Sinisalo - but has he played his way into the team for Sunday's League Cup quarter-final with Rangers at Ibrox?