St Mirren were defeated in their opening Viaplay Cup match at Montrose. Rory McAllister's second-half goal was enough to give the hosts a 1-0 win in the opening Group H match.
Saints had chances to level, but ultimately weren't good enough to take anything from the game and will now be aiming for three wins in the remaining three matches to have a chance of qualifying for the next round.
Manager Stephen Robinson handed competitive debuts to summer signings Zach Hemming, Conor McMenamin and Mikael Mandron.
But it was the hosts who had the first real opportunity of the match when a header from the half-way line caught out the Saints defence and allowed Kane Hester the opportunity to run clear on goal. Charles Dunne did well to use his pace to catch up with the Montrose forward and did enough to put him off as he shot into the arms of Hemming.
Hester was then denied by Dunne just before the half-hour mark after the forward was found inside the six-yard box by Rory McAllister. Hester, Montrose's record signing when he signed this summer, got a flick on the ball in from the left, but the Saints defender was there to turn it behind.
Saints' best chance to open the scoring came with five minutes remaining in the first-half. A corner kick was headed out only as far as Kiltie on the edge of the area and his strike was pushed away by Gill. The Gable Endies goalkeeper was up quick to gather the rebound to deny Kiltie and Mandron as both charged in.
The home side hit the front on 58 minutes after catching Saints on the break. It came after Montrose goalkeeper Gill gathered a corner and launched the ball forward for Mateus Machado. He fed the ball for Hester inside the area before the forward turned and found strike partner McAllister alone at the back post with the experienced frontman firing into the net from close-range.
Despite the set back, the Buddies had an immediate opportunity to equalise when a long throw from Declan Gallagher broke inside the area with Kiltie and Alex Gogic in the immediate vicinity. One of them got a foot on it but knocked over the bar.
Saints had another big chance to level on 65 minutes when Kiltie's brilliant low ball across the face had beaten Gill. Mandron and Greive were sliding in but neither could get the touch it needed to be turned in to the net.
Saints were agonisingly close to the equaliser with less than 15 minutes remaining. Kiltie's strike was saved by Gill but he could only push it into the air and it looked like it may fall into net. Mandron was ready to nod into the empty net, but Montrose's veteran defender Sean Dillon managed to get there first and head over.
Substitute Toyosi Olusanya's trickery won the Buddies a free-kick on the edge of the box in the final moments of the match. To the frustration of the away support, the referee's whistle denied advantage when Mark O'Hara finished into the bottom corner from 20 yards. It was then Caolan Boyd-Munce who stepped up to take the free-kick, but Montrose managed to block and then clear to hold on and claim the win in Group H.
Full-Time: Montrose 1-0 St Mirren
St Mirren: Hemming, Fraser, Gallagher, Dunne (Sutherland 90), Strain, Kiltie, O'Hara (c), Gogic (Boyd-Munce 69), McMenamin (Jamieson 90), Greive (Olusanya 69), Mandron
Subs Not Used: Urminsky, R.Taylor, Kenny, Flynn, F.Taylor
Montrose: Gill, Williamson, Steeves (Machado 21), Quinn, Dillon, Masson, Webster, Brown (Shrive 83), McAllister, Gardyne, Hester (Batchelor 83)
Subs Not Used: Matthews, Grant, Giacomini, Lyons
Referee: William Collum
Assistant Referee: Jonathan Bell
Assistant Referee: Scott Anderson