The 26-year-old spent two seasons at the New Den, making more than 50 appearances, before being released at the end of last season.
It was a decision that definitely irked the former Manchester United youngster, who felt his performances had been worthy of a new deal at the time.
Despite that disappointment though, he won’t be trying any harder against the Lions, saying: “When I first arrived here, that’s one I would have circled on the calendar.
“I’ve still got some friends there that I speak to, so I’m massively looking forward to it, under the lights, at home, live on telly, it’s one to get the juices flowing.
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“I know how football works, it’s a ruthless game, they decided they wanted to move on and that’s that really, no hard feelings.
“It won’t make me try extra harder, I’ll go into the game as I would any other.
“I won’t be trying to make myself look good and shoot on sight, I’ll just play how I normally play and hopefully we get the result.”
It was something that Hatters boss Graeme Jones hopes Tunnicliffe will guard against too, as he said: "A message for Ryan is he doesn’t show any emotion in this game.
"He has to go about his business the same way, as he has done in the previous games and he’ll be absolutely fine.
When asked to pick out the players Millwall possess that Luton should pay extra attention to, Tunnicliffe continued: “They’re a good, solid team, the way they set up, it’s difficult to play against and being there, I know about that.
“Matt Smith’s a handful, proven at this level, he’s a big man. Jez Wallace is a bright spark for them too. Playing with them the past two years, he was always an out ball for us.
“I think those are the people you have to look out for, but they’re a good team, they’ve had a decent start, so it will be a tough game.”
Town are back at home after beating Blackburn 2-1 on their travels at the weekend and Tunnicliffe is urging his side to produce a vastly improved display than their last outing at Kenilworth Road, defeated 3-0 by Hull City.
He continued: “At home, that’s where you’d like to pick up the majority of your points.
“If you get some good home form going, that’s probably how you stay in this league.
“It doesn’t matter who’s coming down, we need to look to win every game we play, and Wednesday’s no different.
“It is massive though, the fans to their credit, stuck with us in that home game (against Hull).
“We collapsed a bit in the last five minutes, which is uncharacteristic, so we need to bounce back and perform for the home fans that have come out every single game, packed the stadium out and give them something to cheer about on Wednesday.”