"With the cup now adopting a straight knockout format from the quarter-finals onwards, the introduction of a fourth substitute in extra time will bring extra intrigue and interest," Glenn said.
"Also, from a technical point of view, it will be interesting to see how managers use the chance to make an additional substitution in such high-profile games and the impact it has on the final result."
This season's competition gets under way on Friday, 5 August when 184 preliminary matches take place.
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Venue: Baltusrol Golf Club, New Jersey Date: 28-31 July
Coverage: Listen on BBC Radio 5 live and BBC Radio 5 live sports extra, with daily live text commentary on the BBC Sport website
World number one Jason Day says he is "running on empty" as he prepares to defend his US PGA Championship title.
The Australian has played only one practice round at Baltusrol after spending Tuesday night in hospital with his wife, who had an allergic reaction.
Day, 28, could lose his number one spot if he finishes 29th or worse and Dustin Johnson is in the top two.
"I'm just a little bit under the weather," said Day, who has topped the world rankings since March.
"I've got to really try and manage my patience out there, because I have very little patience right now. For some reason, every time I get a little bit under the weather, I've got zero patience."
Day's victory at Whistling Straits last year was his first in a major.
He has since finished tied 10th in the Masters, tied ninth in the US Open and tied 22nd at The Open in a season disrupted by illness and injury.
"It's very, very difficult to win golf tournaments," he said.
"I think everyone expects if you're in the lead, or if you're a favourite to win, you will win, and if you don't, then you're in a slump. It's not the case."
John Stones joined Everton from Barnsley for £3m in January 2013
Manchester City are in talks with Everton over the possible signing of England defender John Stones.
A deal is yet to be agreed but it is thought the two Premier League clubs are not far apart in their valuations.
It is thought Everton want £50m for the 22-year-old former Barnsley player, who came close to joining Chelsea last summer.
Stones was part of the England squad at Euro 2016 but did not feature as they were knocked out in the last 16.
He made his debut for Barnsley in March 2012, 10 months before joining Everton for £3m.
City boss Pep Guardiola has identified the Yorkshireman as the kind of central defender who fits his approach to the game.
"Normally central defenders are strong in the air and aggressive," said Guardiola on Wednesday.
"But we need to have a good build-up to create easy passes in the midfield so they can create good passes for the strikers. I believe when the ball goes from the central defender to the striker as quickly as possible, it comes as quickly as possible back.
"That is why the players in that area need quality. By 31 August we will have the right squad to play how we want."
Guardiola used midfielders Javier Mascherano and Javi Martinez as central defenders while managing Barcelona and Bayern Munich respectively.
And the Spaniard has identified a City midfielder who could step into the back four if required.
"Fernandinho can play in 10 positions," he said.
"He is quick, fast, intelligent, aggressive. He is strong in the air and has the quality to play good build-up, can go right or left and can pass long."
One of the two attackers has already been named by police as Adel Kermiche, 19, who had twice tried to reach Syria to join IS.
French investigators believe they are close to identifying the second attacker, according to French media reports.
Officers are said to have found an ID card at the home of Kermiche belonging to an individual named as Abdelmalik P, from Aix-les-Bains in eastern France.
It is not known whether this is the second attacker, whose face was badly disfigured by the police shooting.
Image copyrightAFPImage captionFather Jacques Hamel was killed in his church in Saint-Etienne-du-Rouvray, a suburb of Rouen
France's Le Monde newspaper also reports that French security officials received a tip-off on Friday from an unnamed foreign intelligence partner that an individual was planning an attack in the coming days.
The newspaper says a photograph of the individual was provided but no identity, and French police were hunting for the man in the run up to the attack.
It may be that the so far unidentified man is the dead second attacker, the BBC's Hugh Schofield in Paris says.
French press snubs killer's images
Image copyrightAFP
A number of media outlets in France have announced that they will no longer publish images of people responsible for terror attacks.
In an editorial, Le Monde said it was doing so "to avoid giving posthumous credit" to those responsible, while adding that the intention of killing Father Hamel was to provoke "the blind vengeance that would place the entire country under the empire of hatred".
The move was repeated by the broadcasters BFMTV, France 24 and RFI.
A statement by the joint editorial team of France 24 and RFI said that they were "conscious of the echo that is being offered by our antennae... to terrorist movements who claim a state that does not exist".
The Catholic daily La Croix, which said it was following suit, said in its editorial on Wednesday that "responding to hatred with hatred would mean that evil has triumphed". The newspaper would now give only the first name of attackers, it said.
The Europe 1 radio station announced it would not name perpetrators of terror attacks.
The killing in Normandy came 12 days after the truck attack in Nice in which 84 people died. The Nice killer also pledged allegiance to IS.
