The biggest game of the season so far.

Is that a fair tag to attach to Saints’ FA Cup fifth round trip to Sunderland tomorrow lunchtime?

Too right it is.

Before the third round tie against Burnley at St Mary’s, I wrote in the Echo that Saints need to take this season’s FA Cup seriously.

If they did, it could well turn manager Mauricio Pochettino and his players from men who will be well remembered in 30 or 40 years time into legends.

Now we are down to the last 16, Saints need to take tomorrow’s tie even more seriously.

Victory at the Stadium of Light against a side 15 points and 10 places worse off in the top flight than Saints would propel the club into the quarter-finals for the first time since 2005.

Poch and co would then be just 90 minutes away from a Wembley semi- final. And they could face Sheffield Wednesday or Charlton, Cardiff or Wigan, Sheffield United or Nottingham Forest, Brighton or Hull.

With respect, Saints would be confident of progressing to the semis if drawn – home or away - against any of those teams.

The FA Cup is still the greatest club knockout competition in world football. Always has been, always will be.

Yes, the tournament has been stripped of a little bit of its magic in recent years as the Premier League’s cash cow continues to milk ever more money into the coffers of the lucky elite 20. West Ham’s Sam Allardyce was roundly criticised for fielding a below strength side in a 5-0 pasting at lower division Nottingham Forest. He won’t have been stung by the criticism, and after three successive league wins he won’t care that his team are not in the fifth round this weekend.

Indeed, he has taken his squad off to warmer climes while Saints travel to the chilly and wet north east.

Still, West Ham’s players aren’t in with a great chance of becoming legends overnight this season.

Adam Lallana and the rest of the Saints squad most certainly are.

Jay Rodriguez spoke after the third round win against Burnley that he wanted to go on a long FA Cup run.

And Jose Fonte revealed in this very newspaper yesterday that every single Saints player was taking inspiration from the 1976 FA Cup win.

So they should.

Nick Holmes played over 500 games for Saints, helping the club finish runners-up in the old First Division in 1984.

I would wager a shiny pound coin, though, that he gets more Saints fans wanting to talk about the 1976 FA Cup final he played in.

Same with Mick Channon.

He played over 600 games for the club, twice helping them to a top seven First Division finish in 1969 and 1971.

But how many supporters have ever asked him about those seasons, compared to his day in the sunshine with the rest of the Saints’ FA Cup legends?

Lawrie McMenemy no doubt still comes across people every week who want to talk about the events of May 1, 38 years ago.

And why not? It is still the club’s most famous day.

Fast forwarding to the present, is there a good reason why Pochettino cannot field the same side he did at Hull the other night?

This is the FA Cup. Everyone will be up for it.

No disrespect to the likes of Kelvin Davis and Jos Hooiveld, who have played in both FA Cup ties so far, but Saints will stand a better chance tomorrow if Artur Boruc and Fonte start.

They will stand a better chance if Rickie Lambert is up front, rather than Sam Gallagher. Surely the first choice players are capable of playing twice in five days?

This Saints team has gone to Cardiff, Fulham and Hull in the past few weeks, and kept clean sheets in victories.

Sunderland might be slightly better than two of those clubs in terms of league position, but not much better.

The same Hull side that Saints beat on Tuesday had won at the Stadium of Light three days earlier. I repeat, this is a superb chance for Saints.

They didn’t take the League Cup that seriously when they fielded a below-strength side at Sunderland in the League Cup last November, and paid the price.

Sunderland have since gone on to reach Wembley in that competition.

It could have been Saints.

But the League Cup is dwarfed in glamour and importance by the FA Cup, even if the reward – a Europa League place that Pochettino has already admitted he personally wouldn’t welcome too much – is the same.

Let’s be honest, Saints are going to finish eighth or ninth in the Premier League, and that will be a phenomenal achievement bearing in mind they were losing third division games to the likes of Rochdale less than three years ago.

They are only two points away from equalling last season’s 41-point haul, so have no relegation fears.

Same as 11 years ago, in fact.

Back then, in 2002/03, Gordon Strachan’s side took full advantage of a run of favourable draws to reach the final.

Any Saints fan who was at the Millennium Stadium will forever remember the atmosphere they helped create.

They might have lost the game, but Saints were winners in the stands.

Great memories, even in defeat.

That’s what the FA Cup can provide.

Jose Fonte and the Saints players appear aware of that.

Pochettino has not been in English football that long, but he must be aware of it too.

Win at Sunderland, get a favourable draw, and his players will be desperate to play in the quarters with a Wembley carrot dangling in front of them.

Gus Poyet has overseen an impressive upturn in the Black Cats’ fortunes since he replaced Paolo Di Canio.

But he has a relegation dogfight firmly on his hands, as well as the League Cup final to look ahead to.

Poyet doesn’t need another long Cup run to deflect attention away from his primary goal.

Saints could certainly do with one, though.