Jennings, 26, who averages 25.86 in 16 Tests, was out for 17 and 14 as the tourists lost the first Test by 381 runs.

Denly, 32, who bats at three for Kent, will open with Rory Burns in Antigua.

"It's great opportunity for Joe," Cook told the Test Match Special podcast.

"He's had an interesting couple of years in county cricket, taking on more responsibility at Kent and deserves his call-up. So he will be excited and I will be excited to see how he plays. "

The second match in the three-Test series, at the Sir Vivian Richards Stadium, begins on Thursday at 14:00 GMT.

Cook, who opened the batting with Jennings in his final match for England last September, said the South Africa-born player had been "given a chance as he's played 16 Tests".

England's record Test run-scorer expects Denly to play in the next two Tests in the Caribbean, with thoughts then turning to the team selection for the Ashes series later this year.

"The Ashes is still seven months away so a lot can happen in sport - four Tests, but a lot can happen in that time," Cook added.

"Jonathan Trott came in and did well in a big Test match when we had to win a game and he got 100 - you have to deal with what's in front of you."

Alastair Cook and Keaton Jennings played together in 12 Test matches

Left-arm spinner Jack Leach replaces Adil Rashid in England's 12-man squad. The leg-spinner will return home during the second Test because his wife is expecting their second child.

Rashid will return to the tour before the one-day internationals.

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Of the decision to drop Jennings, England captain Joe Root said "it's disappointing for Keaton".

He added: "[Jennings] has done some very good things and he'll continue to keep developing. He's very much a part of the squad moving forward but it's a great opportunity for Joe."

Denly made his first international appearance since August 2009 in a Twenty20 win over Sri Lanka in October, taking the man-of-the-match award, predominantly for his four-wicket haul.

"Joe is an extremely experienced player who has scored nearly 11,000 first-class runs, he knows his game extremely well and his form over the last two summers in English cricket has been fantastic," Kent director of cricket Paul Downton told BBC Radio Kent. "He fully deserves the opportunity.

"He is a classical player so without doubt he has the game, you just hope he gets a little bit of luck and then that 15 years of being a professional cricketer will kick in."

England 12-man squad for second Test: Rory Burns, Joe Denly, Jonny Bairstow, Joe Root (c), Jos Buttler, Ben Stokes, Moeen Ali, Ben Foakes, Sam Curran, Stuart Broad, James Anderson, Jack Leach.