The 25-year-old, who was released by Sheffield Wednesday at the end of last season, became the Millers' second signing of the summer on Friday when he penned a two-year contract to stay in South Yorkshire.
Mattock played 90 minutes for the Owls in their last-gasp 3-2 win over Steve Evans' men at New York in March.
 |
| Photo from www.themillers.co.uk |
And that stuck in Mattock's mind when Evans made his move.
"I thought of that day when the chance came to sign for Rotherham," he said. "As a footballer, you live to play in matches and atmospheres like that. Yes, I'll have some more of that.
"It's a great stadium. Everything about it is right. I couldn't believe it when I played there last season. It was just so nice, so modern.
"The place erupted when Rotherham scored and the atmosphere was just incredible. I was taken aback at how good it was, to be honest.
"I'm looking forward to that first goal going in at New York Stadium with me wearing a Rotherham shirt, whether I score it or not," he said. "It will be an unbelievable feeling. I know from experience how passionate the Rotherham fans are."
Mattock spent three years at Hillsborough and played 30 times last season in a defence that was the fourth stingiest in the Championship.
He felt that warranted a new deal with the Owls, but jumped at the chance to hop across the M1 and stay in the second tier.
"I was a bit surprised when Sheffield Wednesday let me go," he said. "I'd been part of a good defence and had had a decent season.
"But there were two other left-backs there - Jeremy Helan and Claude Dielna, who's a centre-half but can play full-back - on two-year contracts, so I sensed what might be coming.
"I was on holiday when my agent called and said Rotherham were interested. I thought straightaway that that would be a great move. It was key for me that they were in the Championship.When I got back, I jumped straight on to it.
"I had a great meeting with Steve Evans and knew where I wanted to be playing next season."
