Manchester United will roll into Vicarage Road in full crisis mode at Saturday lunchtime with Louis van Gaal under intense scrutiny despite his side being two points off the top.

It was quickly forgotten that the Red Devils were indeed top of the Premier League standings at the end of September, a 3-0 defeat at Arsenal – one of only two in the league – bringing United back down to earth with a bump.

A win on Saturday will see United return to the summit at the expense of noisy neighbours Manchester City, for a few hours at least, but the problems appear to be stacking up for van Gaal.

The bombastic Dutchman’s style of play has been heavily criticised for being dull and captain Wayne Rooney is struggling to show anything like his best form.

Meanwhile, big summer signing Memphis Depay has been a peripheral figure at best since his £24.6 million switch from PSV Eindhoven with local lad Jesse Lingard ousting him recent weeks, leading to an England call up.

And, just to compound United’s woes, Anthony Martial left Wembley on crutches following France’s defeat to England in Tuesday’s poignant friendly, days after Michael Carrick was injured against Spain.

Here we profile three United players who could make the difference against the Hornets.

Watford Observer:

Juan Mata: With Rooney and Depay struggling to hit the levels expected and Martial likely to miss the trip to Hertfordshire, the responsibility on the Spaniard’s shoulders only increases.

Mata, 27, has been deployed in each of the three slots behind the main striker during his three seasons at Old Trafford but appears to have found a permanent home on the right-hand side of a 4-2-3-1 system under van Gaal.

Brought to United in the 2014 January transfer window by David Moyes, the former Chelsea, Valencia and Real Madrid playmaker appeared in danger of finding himself surplus to requirements once again when van Gaal was appointed last summer.

But with 19 goals in 53 starts the 2010 World Cup winner has become an integral part of United’s forward line and bettered his goal record from his three years at Stamford Bridge, where he struck 18 times in 71 league starts before falling out of favour under Jose Mourinho.

Dangerous set pieces add another string to the Spanish international's bow with his vision, range of passing and ability to unlock a defence all threats in his armoury.

Watford Observer:

Chris Smalling: The England international’s rapid turnaround at Old Trafford has been as impressive as it has been timely.

Along with Phil Jones the former Fulham and Maidstone United centre-back looked destined to become a nearly man at the Theatre of Dreams after a less-than-convincing first few years.

But the 25-year-old appears to finally have put his injury problems behind him and established himself as an automatic starter.

The Greenwich-born defender made just a handful of appearances for Fulham before joining United in 2010 and his rapid elevation was not helped by experienced heads Rio Ferdinand Nemanja Vidic leaving the club in the summer of 2014, thrusting him forward in the pecking order.

Now third captain at United behind Rooney and Carrick, Smalling looks destined to be part of Roy Hodgson’s England squad for next summer’s European Championships in France and is currently in pole position for a starting berth to boot.

Watford Observer:

Bastian Schweinsteiger: The German World Cup winner is just that: a serial winner.

Seventeen trophy-laden years at Bayern Munich came to an end in the summer as the 31-year-old moved for the first time in his professional career to embark on a new challenge in the Premier League having just won an eighth Bundesliga title.

With more than 300 appearances for Bayern and a ton of caps for Germany, for whom he is now captain following Philipp Lahm’s retirement, Schweinsteiger is one of his country’s most influential and recognisable footballers of recent times.

But, thanks to injury, he could no longer call himself an automatic starter under Bayern coach Pep Guardiola and made just 15 Bundesliga starts in his final season at the Allianz Arena.

Snapped up for just £6.5 million this summer, Schweinsteiger became the first German player to turn out for Manchester United’s first team. And, after initial fitness concerns, the organising midfielder has quickly established himself as a vital cog in United’s engine room.