The West Yorkshire club, who finished fifth, booked their place in a Super League semi-final with a hard-earned 8-0 success against last year’s beaten Grand Finalists.
Agar said: “It was a tough, gritty game.
“It’s what we expected. Wigan have been defending very very well and points are hard to come by, especially when we get here and it’s a cold damp night.
“You think points are going to be really really hard to come by and there was a bit of luck in there with our try as well but I love the way we defended.
“We defended really well.”
Ash Handley’s 50th-minute effort was the only try of the night.
If sixth-placed Hull KR beat third-placed Warrington Wolves in the other eliminator this evening, then Leeds will visit champions St Helens next Friday for a place at Old Trafford. If Warrington win, then Agar’s side will head to League Leaders Catalans Dragons on Thursday.
Agar is convinced his players have the right mentality to go all the way to the Grand Final.
“I’m not surprised we’re in the penultimate game because I’ve seen the commitment to each other and their ability to ride adversity,” Agar said.
“We know we’re going to be playing a really good team and what a difficult task it will be to get through to the GF but we’ll give it out best shot.”
Defeat brought Adrian Lam’s tenure as head coach to an abrupt end and signalled the end of the Wigan careers of Oliver Gildart and Jackson Hastings as they prepare to head off to the NRL with Wests Tigers.
Lam said: “I’m absolutely gutted, the dressing room is devastated.
“I don’t know what I’m going to do tomorrow because it wasn’t in the plan. I’ve spent a big chunk of my life in Wigan, I absolutely love the place and I’ve had a great ride.
“I leave with some wonderful memories and I think the club is in a pretty good place.
“We have players leaving too, which is more important than me. We had an opportunity to finish on a fairytale.
“But we didn’t get into our rhythm. We defended pretty tough but we didn’t really attack the way we trained. It’s been a bit like that all year with all the changes we’ve had to make.
“I couldn’t ask more from them - they were gutsy and that’s the way it ends sometimes.”