Forrester, who joined Rangers from Doncaster Rovers in December, did not start the Scottish Championship match against St Mirren on Saturday afternoon.
The 25-year-old former Brentford man came on as a substitute in the 70th minute and scored what proved to be the winner on 86 minutes.
The former Aston Villa prospect has revealed what manager Warburton told him before he went on to the pitch.
“When you are on the sidelines you are there to do a job whenever you are called upon,” Forrester told The Scottish Sun. "The gaffer said go on and make an impact and I did that today, as Nicky Clark did at Kilmarnock.”
Over the course of the 90 minutes at Ibrox, hosts Rangers had 64% of the possession, took 21 shots of which seven were on target, and earned 12 corners.
Visitors St Mirren had 36% of the possession, took eight shots of which four were on target, and earned three corners.
Rangers are at the top of the Scottish Championship table at the moment with 66 points from 26 matches, 11 points clear of second-placed Hibernian.