The Saints and the Baggies are right next to each other in the league table, meaning that a win for either would go a long way to securing their status as the best Premier League outfit outside of the traditionally big clubs further ahead of them.
On the surface, this encounter seems more like a candidate for being last on Match of the Day than a crucial moment in determining how each side looks back on this campaign.
Admittedly, the contest is not very intriguing for the neutral; West Brom and Southampton sit eighth and ninth in the Premier League respectively, and neither are likely to make the European places or be fighting for relegation come the end of the season.
Nevertheless, the match carries the utmost importance for both clubs. With the big boys in Manchester, Liverpool, north London and Chelsea regaining control of the league after last year's bizarre campaign eighth is as high as the Saints or the Baggies can realistically hope to climb.
While not monumental, a top-eight finish would be more than satisfactory for either side, essentially giving them the title of, outside the usual suspects, the best of the rest in England.
With just a handful of games left, the battle for eighth place is set to go down to the wire. West Brom currently hold a seven-point lead on the Saints in ninth, but Claude Puel's men have two games in hand on tomorrow's opponent, meaning victory tomorrow would put them in pole position.
Southampton's inability to finish their chances has been the story of their season, leading to a lack of consistency. However, they will go into the game with momentum, following a morale-boosting 3-1 defeat of Crystal Palace on Wednesday.
In contrast, Tony Pulis' side have gone at a steady, solid place throughout, but a loss at Watford on Tuesday has put their position in the table in jeopardy.
While there are a few teams just below the Saints surely believing that they could still climb up the table, Saturday's visitors' games in hand and their hosts' solid point cushion mean it would be a major surprise if someone else managed to snatch that eighth spot.
Winger Matt Phillips could start for Pulis' West Brom after returning to first-team football from a hamstring injury as a substitute against Watford.
Southampton will be without midfield heartbeat Oriol Romeu as he begins a two-match suspension.
The likes of Steven Davis, Sofiane Boufal, Ryan Bertrand and goal-scoring sensation Manolo Gabbiadini will undergo fitness tests to determine whether they are ready to play after knocks.
West Brom haven't lost in the Premier League since August when they have scored first.
Southampton's shot conversion percentage is 11.1%, the worst in the league.
Only league leaders Chelsea have used less players than West Brom this season.
There's history between them
This time around, West Brom came from behind to win 2-1 on the south coast.
Only Saints striker Shane Long has played for both clubs.