Jamie Walker knows Hearts will need to be quickly on top of their game when they face former boss Robbie Neilson's Dundee United in their Betfred Cup opener.

Neilson returns to Tynecastle on Friday night, less than three years after leaving for MK Dons.

Walker was a key part of the team Neilson guided to the Ladbrokes Championship title ahead of Rangers and Hibernian before leaving them second in the Premiership.

Walker, who has returned to Hearts following a spell at Wigan, said: "When he came in, that was when I started to hit the ground running.

"I have huge respect for Robbie, he came in and took the club back to being an SPL, top-of-the-table team.

"He was great for me and I will probably have a chat with him on Friday.

"They will be coming to Tynecastle thinking they can get something, so we will need to be at it, we will need to be better than we were in pre-season friendlies."

Walker is hoping to shake off a thigh strain to feature for Hearts for the first time in 18 months.

The midfielder's move to Wigan did not go as planned. He arrived there injured and rarely forced his way into the starting line-up, making nine appearances before a loan spell at Peterborough, and no more after undergoing knee surgery in January.

The 26-year-old said: "I'm delighted to be back. It's a club I know very well and as soon as Craig (Levein) gave me the phone call to be back, there was no hesitation.

"I think I am mentally stronger. I have been through a tough time. It's maybe something I lacked when I was here before, being mentally tough.

"I'm feeling fit. I hadn't played or trained for a long period of time due to my knee injury and not being involved down at Wigan. So it's just little niggles that I'm trying to get rid of. But I am hoping to be involved.

"I want to come back and hit the ground running. I want to add to the goals I scored last time, my aim is to get to 50 goals this season."