Pete Cowen revealed he laid down the gauntlet to fuel Brooks Koepka at Shinnecock Hills and can see the American winning more majors after clinching back-to-back U.S. Open titles.
Koepka held his nerve in Long Island on Sunday to become the first man since Curtis Strange in 1989 to successfully defend the U.S. Open trophy.
Cowen, Koepka's short-game coach, warned the world number four he would not realise his potential unless the 28-year-old improved his attitude before he won his first major at Erin Hills last year.
The Englishman, who also coaches the likes of Henrik Stenson and Matt Fitzpatrick, issued another challenge to ensure Koepka was fully motivated ahead of his latest triumph.
Cowen told Omnisport: "I'd been to Memphis the week before last year's U.S. Open and watched him play all four rounds and his attitude and body language was very poor, so I pulled him to one side on the Tuesday at the U.S. Open and said, 'Look, you're not going to win anything with that sort of attitude.'
"I challenged him again this year by saying, 'You want to make sure you keep hold of that trophy, it's a big challenge to keep it so make sure you do.'"
Koepka has established himself as one of the top players in the world and Cowen said he can go from strength to strength.
"He is a very cool character, he doesn't get stressed, he doesn't show any temper, snap clubs... You won't know if he's made a birdie or a bogey on the hole before. He's able to dismiss whatever has happened before almost instantly," he added.
"I've worked with him for the last five years and he's been like that all that time.
"You would say he can win more majors, he's young enough, he's number four in the world now and when you are at that sort of standard you are always capable of winning more. He is very talented and believed in himself [at Shinnecock Hills]."
|Pjanic and Rugani in Juventus tour squad as Ronaldo and World Cup stars are rested|
|Eagle has McIlroy soaring into a five-way tie for the lead at Carnoustie|
|Vettel will not lose any sleep after Hockenheim mistake|
|I manifested my dream – Hamilton revels in Hockenheim win|
|Pakistan seal crushing series sweep of Zimbabwe|
|Furious Ozil accuses German media of turning country against him|
|Woods makes his move as Spieth and Schauffele wobble|
|Vettel crash sees Hamilton retake championship lead|
|RFEF confirms one-legged Supercopa de Espana in Tangier|
|Fognini downs Gasquet to clinch Swedish Open|
|Spieth and Tiger underway as Kisner falls back|
|Iniesta, Torres suffer defeats in their J.League debuts|
|Cornet ends title drought in Gstaad|
|Martial ´very focused´ at Manchester United - Herrera|
|Root, Williamson and Bairstow - hat-trick hero Clark flourishes in Roses battle|
|Sri Lanka spinning towards crushing series whitewash|
|Ozil explains controversial Erdogan meeting|
|It´ll be hard for Tuchel to get our players – Kovac expects Boateng stay|
|Fakhar Zaman fastest to 1,000 ODI runs|
|Neymar happy for World Cup winner Mbappe|
|I was born ready! - Bellew accepts Usyk challenge|
|Tuchel seeks Rabiot answers as Barca rumours persist|
|In-form Storm go top, Rampant Roosters thrash Manly|
|Bancroft discharged from hospital after taking blow to throat|
|MLS Review: Martinez breaks record as Atlanta march on|
|Brewers top Dodgers to snap seven-game losing streak|
|Munguia wins after 12-round marathon with Smith|
|Hart ready to leave City to revive career|
|Puel shuts down Schmeichel transfer speculation|
|Four-way tie at Barbasol Championship as Lincicombe misses cut|
|Lenglet happy not to face Messi|
|Tuchel keen to get PSG stars back after friendly defeat|
|Pulisic signing would interest Klopp|
|Whatever b******t you say, no one forgets – Klopp defends spending comments|
|Usyk outclasses Gassiev to make cruiserweight history|
|Pella books Cecchinato meeting in Umag, Ramanathan´s Newport run continues|
|Kisner expects nothing but exchange of ´horror stories´ with housemate Spieth|
|Inter new boy Lautaro Martinez denies Zenit in six-goal thriller|
|McIlroy eyeing early gains to apply scoreboard pressure|
|The Open 2018 diary: Spieth´s close shave|
|Salah is fully recovered and full of joy – Klopp|
|De Laurentiis accuses Sarri of trying to sign whole Napoli team|
|Lewis Hamilton explains German GP woes|
|O´Driscoll hails ´Test match animal´ Warburton|
|Spieth relishing prospect of Tiger tussle at Carnoustie|
|Sanches pushing for Bayern second chance - Kovac|
|Put on the Sunday red and enjoy Tiger´s ride regardless of Carnoustie outcome|
|Flawless Spieth takes share of Open lead after Tiger winds back the years|
|PSG´s Tuchel to be patient with World Cup stars Neymar, Mbappe & Cavani|
|Sanchez joins United tour in LA after visa issues|
|Catalans crush Salford to confirm Super League safety|
|Hamilton not giving up despite Hockenheim heartbreak|
|Spieth surges into Open Championship lead|
|Dumoulin is our biggest threat – Froome|
|Sane: Low gave me good reasons for World Cup snub|
|Tiger Woods in the hunt and loving it at The Open|
|Vettel delighted with German GP pole performance|
|Deschamps lauds intelligence of ´extraordinary´ Mbappe|
|Thomas maintains advantage as Fraile powers to stage victory|
|Woods sets clubhouse target, Kisner edges back in front|
|Bayern Munich 3 Paris Saint-Germain 1: Sanches strikes in ICC clash|
|Dost re-signs with Sporting CP after initially rescinding contract|
|Impressive Lions see off Jaguares to seal Waratahs semi|
|I´ll show Mourinho I´m ready, says United´s Pereira|
|Fognini sets up final clash with Gasquet|
|Injury ends Bouchard´s Swiss hopes, Sevastova through in Bucharest|
|That didn´t Work-u...race leader pulls up short of 3000metre finish|
|Prowling Tiger Woods on Open charge as Spieth joins leaders|
|Federer will struggle away from Wimbledon - Henman|
|Hamilton expecting tough Sunday at Hockenheim|