Twenty-year-old Mendis was lining up for a strong Sri Lankan Board XI in Colombo and showcased his incredible ability to deliver both right-arm off-breaks and slow left-armers, happily switching from one to the other mid-over with no discernible dip in quality.
Having already made a confident 61, the Galle native proved himself a true all-rounder with his display of versatility but his eye-catching eight-over stint was not enough to distract England skipper Eoin Morgan or Joe Root.
The pair put on an unbroken stand of 174 for the third wicket, finishing not out on 91 and 90 respectively when bad light arrived to bring a 43-run victory via the DLS method.
England had earlier kept a home side featuring nine full internationals to 288-9, with spinners Moeen Ali and Adil Rashid to the fore.
Moeen claimed3-42 as he reeled off 10 consecutive overs in sapping heat at the P Sara Stadium and is more than happy to stick to bowling with one action.
“I’ve never seen someone do that live but it’s great and fantastic for the game,” he said of Mendis.
“It’s amazing he was so accurate with both arms and really it will be the way cricket is going to go. I’ve tried bowling left-arm but I was so bad...you just don’t have that same feel.
“You hear rumours about these guys being around but for him to bowl to that standard and be that good is fantastic.”
A third specialist, Liam Dawson, is expected to get a run out in the second warm-up on Saturday and could have a role to play in the forthcoming five-match series.
“We feel we (spinners) play a massive role to keep it tight and take wickets but these guys are used to these conditions so it might not be as easy for us as people think,” said Moeen.
“At least we do have things in our favour. It was good for my confidence to get a couple of wickets up front. We would like to think we’ll win this series.”