McKenna denies the bottom-of-the-table match being decisive at this stage of the season.
“I've never labelled a game anything like that, whether we've been at the top of the league in the last few years or now, naturally, at the other end,” he said.
“It's January, the game will be on February 1st, but we're in January and there are lots of games and lots of points to play for.
“We see it as an opportunity that we really want to win, that we’re really going to try and win. Southampton will also see it as an opportunity for them to try and win a game.
“But I think whatever happens tomorrow, hopefully, a positive day for us and a positive result, but whatever happens, there's a lot of football left in the season.
“We’ll go at this one with everything we've got, give it everything to try and win the game. Hopefully, we'll do so but either way there's a long way to go.”
McKenna also said: “I think whatever happens on Saturday, I don't know the points totals at the bottom, and that's the truth, but whatever way it goes on Saturday, I'm pretty sure it's still going to be really tight with X amount of games left.
“And the league's really tough. I can watch Southampton's games and certainly over the last six or seven games, they've been competitive in every single game apart from the Brentford game (which they lost 5-0 at home), and Brentford were very good.
“They've gone ahead in a lot of their games and they've conceded some late goals and not quite managed to get the results.
“We know the feeling in the level. The step up, even for Southampton who had had one season out of the Premier League, is really, really difficult and they've done some good things, they've signed some good players, they've got some of the players from last year, but they haven't quite found a way to consistently pick up points at the level.
“The margins to do that are really, really small. We know their qualities as a team and we feel that there are areas that we can go and try and hurt them.
“I'm sure they'll do the same for us as a team, but we'll go into the game with the utmost respect for the opponent and, other than that, focus on giving the best performance we can.”