Sheffield United: 'It's disrespectful!' - Blades star Mark Duffy responds to supporters he feels are 'questioning his professionalism' by doubting fitness levels

The 33-year-old has made 26 appearances for Chris Wilder's side this season - but has completed only two of the games he has started.

Duffy played 66 minutes of United's 1-0 defeat at Swansea on Saturday, and made his feelings clear on social media towards fans he feels are questioning his level of fitness.

"I find it very disrespectful that people question my fitness levels," Duffy said.

"By questioning that, you're questioning me as a professional and the hard work I put in every single week.

"But let me make it 100 per cent clear. I can play for 90 minutes, 100 per cent.

"And the day I can't, I'll retire from the game."

Earlier in the season, Duffy revealed he is towards the top in United's running stats and added: "I can last the minutes.

"A while back, when I kept getting taken off, the lads gave me a bit of banter. I resisted the temptation to chuck those stats back at them.

"But seriously, the gaffer saw I was a little bit disappointed to get subbed once so he had a chat with me and said he didn't want me getting subbed.

"I wasn't disrespectful, it was just me showing my emotions because I want to be out there helping. But that was a great touch from him and that's another thing about here: the honesty of the place."