If those comments were a warning to Morelos, it was one well heeded by the Colombian, who scored the winner in the 18th minute with a cute glancing header and was a constant thorn in the Croats' sides on Thursday.
"I thought his performance was selfless," said Gerrard, who was in charge of Liverpool's academy before taking up his first senior managerial position in Scotland in May.
"I thought he ran his socks off for the team, and the defenders and goalkeeper are thanking him and giving him credit for the shift he put in for us."
Rangers infamously went out in the first round of last season's competition at the hands of Luxembourg part-timers Progres Niederkorn, and while they are in the box-seat for a place in the third round, Gerrard said they must take nothing for granted at home next week.
But the former England skipper was clearly pleased with the organisation and effort his side showed in Croatia.
"Tonight wasn't a performance in terms of our attacking players, it wouldn't have looked great on the eye, but that's how you get success in Europe," he told RangersTV.
"You've got to come to places like this and weather the storm, come and be difficult to play against, and not concede goals and try and get something the other end."
Should Rangers advance to the third round, a match-up against Slovenians Maribor or Georgian side Chikhura awaits.
(Writing by Peter Rutherford in Seoul; Editing by Ian Ransom)
