Mackie joined the Reds from Sky Bet Championship rivals QPR last week on a three-year deal and the 27-year-old forward is relishing the prospect of running out at the City Ground on Saturday against Huddersfield.
He told the club's official website: "It is probably the most excited I've been for a long time to play football and get the season started. I've been driving past the City Ground back to where I stay and it looks the perfect place for me to play my football.
"I can't wait to see it packed out with fans on Saturday and to get playing in front of them. I've really enjoyed training with the lads so it'll be great to get the shackles off and hopefully start the season with a win.
"I've settled in really well, the facilities are great and I've enjoyed coming into training every day. There is a great environment here, the lads have helped me settle in quickly and now it is time to focus on Saturday's game."