U.S.-based Englishman Casey, who appeared in the biennial event in 2004, 2006 and 2008, is ranked 12th in the world but does not have European Tour membership and is therefore ineligible for the team.
Scot Knox, who is also based in America, is 19th in the rankings and was overlooked by captain Darren Clarke for one of the three wildcard picks.
"I don't think Darren had the best team," Jacklin told Reuters in an interview after holders Europe lost 17-11 to the United States at Hazeltine National on Sunday.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"The likes of Casey and Knox should have been in the team. Future captains need to have the 12 best players at their disposal - we need to look at the system.
"The European Tour should have rules that are conducive to being able to pick anybody born in Europe," said Jacklin who was described by ESPN last week as the man who saved the Ryder Cup when interest was waning at the start of the 1980s.
"Having to be a member of the tour in the modern-day game is a bit confining."
The 72-year-old Englishman believes the team should comprise eight automatic selections from the world rankings and European money list, with the captain having four wildcard choices rather than the existing three.
"If you've got four picks you're not keeping anyone out," said 1969 British Open and 1970 U.S. Open winner Jacklin. "You want good match players and it gives the captain options.
"You can't afford to waste any places in the team. The Americans had a better side this time, no doubt about it."
Europe's team at Hazeltine featured six rookies and two of them played exceptionally well.
PIETERS PRAISE
Big-hitting Belgian Thomas Pieters was the top scorer on either side with four points while Spain's Rafa Cabrera-Bello picked up two and a half points from three games.
"Thomas is a potential world number one," said Jacklin. "He is a fantastic player, what an incredible Ryder Cup initiation.
"Rafa was marvellous too. They are two wonderful examples of what a first-timer can do. What a change of life for them to know how well they settled in to the team," added Jacklin, an ambassador for the Farmfoods British Par 3 Championship.
"It must give them enormous confidence for the future and they should take great credit for their performances."
Jacklin, Europe's most successful captain after leading the side to two victories and one tie in four matches in charge from 1983-89, said this year's event was a fitting tribute to the great Arnold Palmer who died five days before the competition started.
"It was a spectacular Ryder Cup and the best team won," he added. "There was a barrage of birdies and in the first hour and a half of Sunday's singles the players looked as though they had the ball on a string.
"It was played in completely the right spirit and that's what makes it such a unique deal. The spectators go over the top sometimes but when they see the players embracing and congratulating each other like they did, it's the right balance.
"It was fantastic to watch, sportsmanship at its best, gentlemanly conduct all the way through. What other sport can show that? None that I know," said Jacklin.
"What a send-off for Arnold. The event was dedicated to his memory and it will go down as one of the great Ryder Cups."
(Editing by Ed Osmond)
