The fourth round of the FA Cup is upon us and there are some big matches and possible upsets on the cards. All games can be streamed LIVE on ESPN+ in the U.S; Nick Miller previews the action and what to expect.

Jump to: Best chance for an upset? | Best game to watch? | The long shot | The curiousity | The derby

The big questions

Is the FA Cup Jose Mourinho's priority?

Obviously we would never suggest that Jose Mourinho would think about what's best for him rather than his team, but Tottenham's FA Cup campaign raises an interesting question. There are already doubts about his tenure and stories being leaked to the media about dissatisfaction within the squad, but would winning the FA Cup -- Tottenham's first trophy for 10 years and one more trophy that Mauricio Pochettino ever won -- change things?

It wouldn't mean Mourinho replacing Pochettino in the affections of most at Spurs, but it might lead to him being granted a little more legitimacy, patience and respect. Qualifying for the Champions League will still be their priority (they're six points behind a stumbling Chelsea) but Mourinho will place a lot of emphasis on success in the FA Cup, too, for the good of the team, as well as himself. Southampton, who have hit some form of late, will prove a tough obstacle to that path, though (live on ESPN+, Saturday at 10 a.m. ET)

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Which kids will Liverpool play?

As the merciless red juggernaut ploughed through another unsuspecting opponent on Thursday, Liverpool's thoughts were a fair distance from a game against Shrewsbury at New Meadow on Sunday evening (live on ESPN+ at 12 p.m. ET). The Reds still have a few Premier League and European opponents to flay before their A-team concerns themselves with the FA Cup, so it will be back to the youngsters for a trip that Jurgen Klopp could probably do without, regardless of who plays.

But who will we see face the Shrews? The likes of Harvey Elliott, Curtis Jones and Nico Williams will presumably get a chance, but it will be interesting to see which fringe players Klopp uses. He will be conscious that there are still potentially 22 Premier and Champions League games remaining in the season, and he might look at the injuries suffered by key men elsewhere (as well as James Milner falling lame in the third round) and reason that he can't even risk the likes of Divock Origi, Adam Lallana and Joel Matip. The team sheet will be awaited with interest.

How will Manchester United cope with Tranmere's cabbage-patch pitch?

They were blow-drying the Prenton Park pitch this week, as Tranmere desperately tried to get it ready for their terrific third-round replay win over Watford on Thursday. The pitch has caused some problems this season, being on the end of fierce criticism by Chelsea Women's manager Emma Hayes and of course being deemed unsuitable for the first attempt at that Watford replay.

It's a drainage issue that won't be fixed until they can completely dig it up in the summer, but playing two games in four days will hardly help matters with Manchester United the visitors on Sunday (live on ESPN+ at 10 a.m. ET). Odd as it might seem, given the week United have endured, they would surely have preferred to visit the lush and familiar surrounds of Watford rather than the uncomfortable Tranmere this weekend.

The best chance for an upset

Brentford vs. Leicester (live on ESPN+, Saturday at 7.45 a.m. ET)

Admittedly, there are bigger gaps this weekend than between the sides third in the Premier League and fifth in the Championship, but if it's a lower-division team potentially beating a higher division team you're after, then Griffin Park on Saturday is probably your best bet. It will probably be the best game of the fourth round, too -- two teams defying expectations at the business end of their respective leagues going head-to-head.

Brentford are arguably the most impressive club in England, using a combination of traditional scouting and data analysis to create a buy low/sell high system whereby they lose their best player every season, but are getting better. Last season it was Neal Maupay, sold to Brighton, but they're now right in the hunt for promotion and could be playing Premier League football at their new home next season. It will be an upset, but not a huge shock if they beat Leicester.

The game you weren't planning to watch, but should

Millwall vs. Sheffield United (live on ESPN+, Saturday at 10 a.m. ET)

Clearly the most boring FA Cup draws are between two moderate teams in the same division, while close behind are ties between sides that have very recently been in the same division. But Sheffield United's trip to Millwall is more interesting, if only to see whether Millwall can keep up their remarkable record in the FA Cup: They have reached the quarterfinals or later in three of the past seven seasons, which is seriously impressive for a team who have spent most of that time at either the wrong end of the Championship or in League One.

The Den is your archetypal "tough place to go" and Chris Wilder will realise that, so he will have to weigh up his priorities when selecting his team for the trip to south London.

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The long shot

With Tranmere facing Man United, Shrewsbury against Liverpool, and Oxford United hosting Newcastle (live on ESPN+, Saturday at 10 a.m. ET), there are a few League One vs. Premier League encounters, but the lowest-ranked team left in the competition are League Two's Northampton Town, who face Derby County on Friday (live on ESPN+, at 3 p.m. ET).

If you consider their form, this should be a pretty decent encounter: Both Northampton and Derby have won four of their past six, the former knocking on the promotion door in the fourth tier, while the latter recover in the Championship after a worrying few weeks when they appeared to be getting into a relegation tussle. If it's a true upset you're after, this is the place to concentrate.

The curiosity

Here's a strange one for you. League One Coventry City are Birmingham City's tenants this year, playing at St Andrew's while their exile from the Ricoh Arena -- nominally their home stadium -- continues. But they were drawn at home in this round ... to Birmingham (live on ESPN+, Saturday at 10 a.m. ET). So the Blues are playing away in their own home, hosted by the team that doesn't have a home. The game is sold out, but the teams agreed to a near-50/50 split in tickets, so this will feel a little like a low-profile semifinal at a neutral venue, except that neutral venue will be both teams' home ground. This could get confusing.

The derby

West Brom and West Ham (live on ESPN+, Saturday at 10 a.m. ET) are separated by a little over 100 miles and a division these days, but this one carries some interest because of the man in the Baggies' dugout.

Slaven Bilic spent two seasons as a player and two and a half as manager at West Ham, but after he was dismissed a couple of years ago took on the challenge of getting West Brom back into the Premier League. It was going pretty well until a few weeks ago, when their form suddenly disappeared, and their previously massive lead in the promotion race has dwindled to virtually nothing in recent weeks. The FA Cup might thus come as a handy distraction for West Brom, but for Bilic this game will mean a bit more.