Luton are unbeaten in six Championship games and had won the previous three before the trip to Wearside.

"I've got one of the cushiest jobs in the middle of a [back] three and even I was struggling," Lockyer said.

"We weren't at it 100%, there were a few leggy boys there, it's been a really tough period.

"We've got the GPS data coming back from the games and I don't know how some of the boys do it.

"[There's been] A lot of travelling, a lot of games, a lot of heavy legs and when the [Sunderland] crowd got going, it was really tough.

"It would have been nice to go into this break with a win but sometimes you don't always get what you deserve in football," he told BBC Three Counties Radio.

The Hatters are fourth in the table - six points adrift of Sheffield United in the second automatic promotion place, but importantly, seven clear of Norwich in seventh place with only eight games left to play.

They were unhappy with the 86th-minute penalty awarded to Sunderland - earned and scored by substitute Amad Diallo.

Boss Rob Edwards described it as a "wrong decision" but Lockyer chose to keep his thoughts to himself.

"I wish I could tell you exactly how I feel, but you're not allowed to do that nowadays," he said.

"Watch it back - if I say any more I run the risk of getting into serious trouble."

There will be little rest for Lockyer during the break as he is in the Wales squad for European Championship qualifiers away to Croatia and at home to Latvia.

"I had a long time out of the Wales set-up before the World Cup so it's really nice to be back part of it," he added.

"I'm a very patriotic man and in footballing terms, every decision I've made in my career has been with the view in mind of giving myself the best chance of playing for Wales."