Morgan, who suffered from a back spasm in the previous game against West Indies, didn't seem to be in any sort of discomfort as he smashed record-shattering 17 sixes in his knock of 148 to help England post a humongous total of 397/6 on Tuesday.
Afghanistan, who were never in the hunt, still came out with a decent batting performance but the scoreboard pressure never allowed them to break free as they managed to post 247/8 in their full quota of 50 overs.
Morgan, adjudged the Player of the Match, said everything went England's way from the start in Manchester.
"Today was fantastic for us. The wicket was very good. I thought everything from the way we started - our openers started well. (Jonny) Bairstow and (Joe) Root were excellent, and then we just took a gamble and it paid off," said Morgan at the post-match presentation ceremony.
"I didn't really think it was going to be my day at any point to be honest. I've had a bad back and it looks like I'm getting old. There are many guys in the dressing room and who can produce an innings like that - but to match up to the youngsters is amazing. I didn't think I could produce an innings like that, honestly," added the 32-year-old.
During the course of his 71-ball innings, Morgan went past 200 sixes in ODIs and raced away to his 13th ODI hundred and his first in a World Cup.
The England skipper also revealed that he has brought in some changes to his game which are paying dividends for him.
"I have changed in terms of my game - every one plays the shots I started my career with - the scoops and the sweeps, etc. However, right now, I'm stronger down the ground than I have ever been, and life seems to have come full circle that way, because cricket has evolved in a way that there are fields that the oppositions set for those funky shots now."
With the win, England are now at the top of the table with eight points from five games. Next the tournament hosts will face Sri Lanka (June 21), Australia (June 25), India (June 30) and New Zealand (July 3).
"The next two-three games are pretty crucial. We want to bring that level of intensity in every game we play. We don't want to slack off," he insisted.
( With inputs from IANS )
