The 21 year old Nigerian youth international was signed from Roma on loan in the summer and is widely considered to be a talented prospect, but questions over his attitude have plagued him so far in his young career.
Gerrard said the youngster would have to improve ''everything'' and ''come to the party'' if he was to feature for Rangers and many considered this to mean he was unlikely to play much this season.
However with Alfredo Morelos out injured and Kyle Lafferty suspended, Gerrard has extended the olive branch to Sadiq after improved performances in training.
Speaking ahead of Rangers' trip to Hamilton on Sunday Gerrard said of the attacker: "Umar has shown that improvement. He's been working very hard. He's got his head down, he's improved a lot.
"His application has improved, his quality has improved so he's given me something to think about for the future.
"I don't know [if the warning has sparked the change], that's something you'd have to ask Umar. But sometimes when a manager is honest with you, sometimes you have to go away and self-reflect.
"If you're a proper footballer you go analyse and come back stronger."