Montgomery took his Hibernian side to Celtic on Wednesday night in the Scottish Premiership looking to continue their good form and cause a shock.
Things went wrong for Hibs after just five minutes with Celtic pulling ahead, while Matt O’Riley then made sure the hosts went in 2-0 up at the break.
Oh Hyeon-gyu grabbed his second in the 55th minute, just four minutes after Luis Palma scored from a penalty.
Hibernian grabbed a consolation through Christian Doidge to make sure Celtic did not secure a clean sheet, but headed back to Edinburgh on the back of a big beating.
Montgomery though is remaining upbeat and insists that Celtic did not carve his defence open, while he thinks the spot-kick the Bhoys were awarded was a soft one.
“The most disappointing thing was the manner of the goals we conceded”, he told BBC Scotland.
“They never carved us open really, it was our own doing, just poor defending. The first two goals are totally avoidable.
“We had two one-on-ones in the first half. If one of those goes in, it gives us a chance to get back into the game.
“Second half, we started brightly and, for me, it’s a soft penalty
“I’ve lost count of how many incidents like that we’ve had and they never go to the screen.”
Montgomery will now focus on preparing his men for a trip to bottom of the table Livingston, the first of a run of three more away games, with St Johnstone and Ross County to come after.