With the bulk of his squad away on international duty, Guardiola took the unusual step of promoting Trograncic from Bayern's Under-15 squad to train with the seniors on Friday.
The teenager ran out alongside the likes of ex-Germany captain Philipp Lahm plus Brazil defenders Rafinha and Dante in front of 200 spectators at Bayern's training ground.
Despite being just 1.50m tall (4ft 11ins), the pint-sized midfielder held his own, going hard into a tackle on Lahm, drilling home a penalty and earning praise from Rafinha.
With Guardiola having given the rest of the squad time off until Tuesday, Friday's session is likely to be a one-off for baby-faced Trograncic, who will not be involved in Bayern's Bundesliga clash at Borussia Dortmund on Saturday.
Trograncic, who has played four matches for Croatia's Under-14 side, spent two years at Red Bull Salzburg before joining Bayern.
The German Football Association (DFB) has invited him to a training session with the junior squads.