Having had a cardiac ablation to correct the problem, the 36-year-old says he is now "healthy" and focused on making his comeback for United.

He wrote in a statement posted on Twitter: "I just want to clear up my situation as I've had quite a few people asking if I'm OK and why I haven't been fit over the last couple of months.

"After feeling strange during the second half of the Burton game in September I underwent a series of tests. It turned out to be an irregular heart rhythm which has been fully investigated and I had a procedure called a cardiac ablation.

"I had to build up training steadily while being monitored closely but I feel fine now.

"I would like to reassure everyone that I'm healthy and back training hard with the team. I'm building up my fitness and aiming to be back in contention for selection soon."

The British Heart Foundation describes ablation as using either heat or freezing on the areas of the heart that cause an abnormal rhythm.

BHF adds on its website: "This treatment creates scar tissue which breaks abnormal circuits in the heart (and) destroys areas of the heart muscle which are triggering arrhythmias."

Carrick has been a key presence at the centre of United's midfield for over a decade, having joined from Tottenham in an £18m deal in the summer of 2006.

He has made more than 400 appearances for the Red Devils and his trophy haul includes five Premier League crowns and FA Cup and Champions League triumphs.

After he signed a one-year deal in May to extend his stay at Old Trafford until the end of this campaign, United manager Jose Mourinho labelled the veteran as "one of the true professionals of the game".

Carrick made 38 appearances, including 18 Premier League starts, last season and was made club captain over the summer following the departure of Wayne Rooney to Everton.

"We wish Michael well and look forward to seeing him back on the pitch soon," the club said.