Brooks Koepka salutes caddie after Bryson DeChambeau parts company with his bagman

Bryson DeChambeau began his defence of the Rocket Mortgage Classic a day after the sudden departure of his caddie, which prompted Brooks Koepka to fan the flames of the ongoing feud between the pair.

DeChambeau surprisingly parted company with Tim Tucker on the eve of the tournament, a split confirmed by the American's agent who appeared to insist that the decision was mutual.

Tucker had been on the bag for DeChambeau for all of his eight victories on the PGA Tour, including his maiden major at the US Open last year, and he caddied as usual during this week's practice rounds at the Detroit Golf Club.

But it became apparent that the relationship between the pair had become strained over recent months, with DeChambeau struggling for form since winning the Arnold Palmer Invitational and then posting a podium finish at The Players Championship in March.

"They had a good run, and they mutually agreed yesterday afternoon to go their separate ways," DeChambeau's agent, Brett Falkoff, told the Golf Channel on Thursday morning.

"Everything runs its course. Tim was getting tired and Bryson was getting tired. In any relationship they run their course, and that's what happened here.

"It wasn't one specific issue. It was a culmination. Like any caddie-player relationship, they had their ups and downs. They wish each other nothing but the best and will always be there for each other."

Koepka, whose rift with DeChambeau was revealed during the PGA Championship in May, then took to social media to salute his long-time caddie, Ricky Elliott, and declaring Thursday as "caddie appreciation day".

"Couldn't do it without my guy Rick," Koepka wrote on his Twitter account. "Best friend and greatest caddie to do it."

DeChambeau had Cobra Golf tour operations manager, Ben Schomin, on his bag when he finally got his first round under way following a delay of over three hours due to adverse weather in Detroit.

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And the late change of caddie may have contributed to a poor performance from the defending champion as he offset three birdies with three bogeys on the front nine and then parred every hole on the inward run, a level-par 72 leaving DeChambeau outside the top 100 and needing a big second day to avoid missing the cut.

The world No 6 finished his first round moments before play was suspended due to darkness and nine shots behind surprise leader Davis Thompson, playing in only his third event since turning professional and firing a course-record 63 with nine birdies and not a single blemish on his card.

England's Tom Lewis enjoyed a positive start with a 65 earning him a share of second and lifting his hopes of earning a spot at The 149th Open at Royal St George's, where he famously shared the first-round lead while still an amateur in 2011.

Ireland's Seamus Power birdied his last three holes to card a 66, while Jason Day defied his aches, pains and allergies to fire a 67 along with Matthew Wolff, with former Masters champions Danny Willett and Bubba Watson one shot further back.