He was dropped after making 37 in the first game against Afghanistan last week which, he said, made him understood what he has to do to keep his place.
Imrul, a regular opener, was made to bat at No 3 against Afghanistan and though he was hitting the ball nicely, he did not last too long and subsequently lost his place. Soumya Sarkar, however, continued as Tamim Iqbal's opening partner despite making 31 runs in that ODI series.
With Bangladesh having decided that Sabbir Rahman will be their No. 3 against England, Imrul and Soumya are contesting a single opening slot. Both were sent to open in Fatullah in this practice game in what turned out to be a bat-off.
"There is a lot of competition for places in the Bangladesh team," Imrul said. "You have to do something extraordinary to stay in this team. You can't stay if your performance is average. I played the first ODI but was left out for the next two and I felt that maybe I need to do something better, which is why this innings feels really good.
"It was not an international match but the atmosphere was similar. I needed an innings like this after a long time. It is definitely a big confidence boost to score a century against a team like this."
In Fatullah, Imrul was unusually attacking during his 91-ball innings. He started off with a flurry of boundaries before seeing Soumya beaten by Chris Woakes' pace in the fifth over. He continued the attack, and reached his hundred off just 81 balls.
He has credited coach Chandika Hathurusingha, who told him to be in a frame of mind in which he is ready to play shots square of the wicket on both sides. According to Imrul, the changed mindset kept him alert to put away every bad delivery. With plenty on offer, he struck 11 fours and six sixes.
"The mindset was very important. My mindset in the last few matches was to stay at the wicket. Today I was positive from the start and I connected well with the first ball. In the last two days the coach gave me some very good advice which helped.
"He told me to be prepared to play the cut and pull, and then maybe take singles off good balls. Your body will always be positive and you will react quickly. I practised that in the last two days, so for that my balance, everything was positive," he said.
Mohammad Isam is ESPNcricinfo's Bangladesh correspondent. @isam84