International Friendly: Luxembourg 1 Turkey 2
The Bayer Leverkusen ace has been in fine form for his club this term, though Terim has often opted to leave him waiting in the wings as he did for Saturday's 1-1 draw with the Netherlands, but he proved decisive at Stade Josy Barthel.
Terim made a host of changes from the weekend, seemingly bowing to pressure from supporters to start Calhanoglu and things began well, Mevlut Erding brilliantly opening up an early lead.
The away side unsurprisingly dictated the tempo, though Luxembourg looked a danger on the counter-attack and they went into the break level thanks to Mario Mutsch's precise finish just after the half-hour.
Having earlier rattled the bar as Turkey's attempts to retake the lead looked set to end up fruitless, Calhanoglu's 30-yard drive took a deflection and looped into the net with three minutes to play.
Calhanoglu was just one of nine changes in Terim's team but they started strongly, despite the upheaval, moving the ball with fluidity and seizing the early initiative.
It took Turkey just four minutes to make their superiority tell, Erding catching Jonathan Joubert off his line with an exquisite lob from 25 yards.
Turkey continued to control proceedings, though they failed to build upon their early opener and the hosts punished them to draw level with 32 minutes on the clock as Mutsch was allowed to charge unchecked up the right flank and he eventually tried his luck from 25 yards, striking across the ball and seeing his effort go in off the left-hand post.
Turkey almost retook the lead five minutes before the break, as Erding's clever flick landed kindly for Olcay Sahan near the penalty spot, but Kevin Malget produced a vital block to halt the danger.
Terim introduced Volkan Sen and Umut Bulut from the bench at the break and the former looked Turkey's best bet in front of goal, forcing Joubert into diving save almost immediately, before blasting just wide in the 57th minute.
Luxembourg retained their threat, however, and nearly took the lead themselves four minutes later, Laurent Jans seeing his effort headed clear just in front of the goal-line by Ozan Tufan.
Turkey continued to pile on the pressure towards the end, with Calhanoglu's set-pieces proving problematic.
But it was from open play that the Leverkusen star made the difference, seeing his effort from distance strike a defender and fly past the helpless Joubert, though the win will likely leave Terim with more questions than answers.