Jordan followed another demonstration of his increasingly familiar clean hitting in England's 247 for six, between the downpours in London, with three for 25 as Sri Lanka's reply fell well short of a twice-revised target in the rain-reduced contest.
Others deserved honourable mention in an especially promising display from England - including new number three Gary Ballance (64) Ian Bell (50) with half-centuries, and three wickets too for James Tredwell.
But Cook was in no doubt about who had made the most difference.
"It was a fantastic performance," he said, of Jordan's 38 from 13 balls and his spell of three wickets for three runs at a critical stage of the tourists' faulty chase.
"To come in and whack it like he did - he hit a really clean ball, against a very good death bowler [Lasith Malinga] - was a credit.
"That extra 30 odd we got in the last two overs gave us that momentum swing we really needed.
"Then he probably didn't start off as well in the first two overs (with the ball).
"But when he came back, he flew in and he bowled quickly.
"Those wickets he got, it looked very uncomfortable batting."
Jordan's contribution was enthusiastic as well as skilful - just what England want from their emerging players at the start of this much-touted new era, under returning coach Peter Moores.
"You want to see people enjoying themselves ... and I hope people can see that passion," added Cook.
"It was (impressive). We played really well.
"Everyone contributed to the performance, and that's important.
"We handled the conditions, and the change of the game, very well.
"I've always said there's a lot of talent there, and the guys have been given an opportunity.
"It's up to them to take it.
"They've been given first crack of the whip, and over the last couple of (ODI) games the youngsters have really stood up."
Ballance falls into that category, and he too pressed his claims - having inched out Michael Carberry to bat at number three.
"It was a tough call between Gary and 'Carbs' to play. Gary got the opportunity, and obviously took it very well," said Cook.
"He's very composed and certainly knows his game. That's what impresses me.
"We certainly haven't seen the best of him either (yet). His record for Yorkshire is almost second to none.
"He averages well over 50 in both forms of the game, and not many people do that anywhere.
"He will find his feet more and more in international cricket. He's certainly got the package to excel."
Cook's opposite number Angelo Mathews had much less to smile about, and did not hide his disappointment that the tourists were unable to follow up Tuesday's Twenty20 win at the same venue.
"We were never really there, from the beginning," he said.
"Our bowling was a bit scrappy, and also we never really got going with our batting.
"All in all, I thought it was a really poor performance by the whole team."
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