In case you've been living under a rock for the past few days, the five-time major champion ran after a still moving putt and hit the ball back towards the hole during Saturday's third round - his 48th birthday - and incurred a two-stroke penalty.

Many, however, believe the USGA should have disqualified Mickelson after he admitted he deliberately incurred a the penalty rather than risk running up a bigger score, sparking criticism that his actions were not in the spirit of the game.

Read more - Day 'disappointed' by Phil & USGA

Wow. I've never seen that before.

Phil Mickelson ran after his putt before it stopped, which is a two stroke penalty.

Really, really odd #USOpenpic.twitter.com/Hu08036qjo

— Cam Rogers (@MrRogers99) June 16, 2018

OPINION - Phil Mickelson should have been DQ'd

Speaking afterwards, he told reporters that anyone offended by his action should 'toughen up', before adding: "I was just going back and forth and I'd gladly take the two shots over continuing that display.

"No question it was going to go down into the same spot behind the bunker. You take the two shots and you move on. I was taking advantage of the rules."

Now, Mickelson has apologised for his actions in a text message sent to a group of reporters, one of whom was Dave Shedloski of Golf World, who shared Mickelson's comments in this tweet.

Read more - Chamblee rips into USGA

Just received a note from Phil Mickelson. “I know this should've come sooner, but it's taken me a few days to calm down. My anger and frustration got the best of me last weekend. I'm embarrassed and disappointed by my actions. It was clearly not my finest moment and I'm sorry. “

— Dave Shedloski (@DaveShedloski) June 20, 2018

Phil Mickelson apologises - Your thoughts

Fair play to Phil Mickelson for apologising for his action - but is it too little, too late in terms of restoring some of his reputation? Let us know in the 'Comments' section below.