The Gunners fell to another away defeat last time out in the league to lose their place in the top four, and they cannot afford to drop more points against the 2019 FA Cup finalists.
Watford supporters will probably still be pinching themselves a week on from their magical FA Cup semi-final victory over Wolverhampton Wanderers. With 11 minutes of the match to play, the Hornets trailed 2-0 and looked out of ideas.
A world-class strike from Gerard Deulofeu started a memorable comeback, though, which culminated in the Spanish attacker slotting the ball home in extra time after Troy Deeney had levelled from the spot 94 minutes in.
No matter what happens from here, this will go down as one of the finest seasons in Watford's history. As well as having a cup final against Manchester City to look forward to, Javi Gracia's side are also still in contention for a seventh-place finish in the league.
Europa League football at Vicarage Road is therefore a real possibility for Gracia and his side, but they still have a couple of tough fixtures - against Arsenal and Chelsea - to come before the end of the season.
Leicester City's defeat to Newcastle United on Friday night was the perfect start to the weekend for the Hertfordshire outfit, leaving them one point off seventh with two games in hand to play on the Foxes.
Watford's most recent league outing finished in a 4-1 win over Fulham on April 2 when producing an improved second-half display to relegate their opponents. That followed back-to-back away losses to the Manchester clubs, which Gracia would have lost no sleep over.
The Hornets' home record has been solid all season, going five matches without defeat at Vicarage Road in the Premier League and winning the last three in a row there. Not since December 1986 have they won four successive home top-flight matches in the same season.
Supporters' focus may well be on the FA Cup final against Man City on May 18, but for now Gracia must keep his players grounded and keep them on course for seventh. With two avenues still open for Europa League football, fans can start dreaming of European football returning to these parts.
Recent form in Premier League: WLWLLW
Recent form (all competitions): WLWLWW
Defeat to Everton aside, Arsenal have been in terrific form over the past couple of months, taking 21 points from a possible 30 in the top flight and progressing through two knockout rounds of the Europa League.
Thursday's 2-0 win over Napoli means that the Gunners have one foot in the semi-finals of the European competition, but their poor away form this term does leave some doubt in the mind.
In the league, Arsenal have won 14 and drawn two of their 17 home matches - losing only to Man City on the opening weekend - while away they have accrued just 19 points from a possible 45, placing them below opponents Watford in that regard.
Arsenal are also yet to keep a clean sheet away from home in the Premier League this season (15 games) - the only side yet to do so - and last had a longer run without a clean sheet on the road in the top flight between April 1984-February 1985 (16 games).
Emery, who once went an entire season without an away league win at Sevilla, has seen his side win just one of their last nine league matches away from the Emirates Stadium and two out of 12 in all competitions.
There is no doubt that Arsenal have a real problem on their travels, which Emery desperately needs to get to the bottom of. Of their last six league matches, four of them are away from home.
That is why, despite the North London outfit sitting in a healthy position, supporters are not so confident of landing a place in the top four. If Arsenal are to improve on last term's final position under Arsene Wenger, they quite simply have to start picking up three-point hauls on their travels.
The good news for the visitors is that they have won seven of their last eight Premier League games on a Monday, losing only against Crystal Palace in April 2017 in that run. Opponents Watford, by comparison, have only won two of their 15-such fixtures - a 4-2 win over Portsmouth in April 2007 and a 4-1 victory against Chelsea in February 2018.
Recent form in Premier League: WWDWWL
Recent form (all competitions): LWWWLW
Emery must decide whether to use Granit Xhaka from the off or instead give the Swiss midfielder some more time to recover from a troublesome injury.
In terms of the hosts, Deulofeu has surely earned the right to start following his incredible display from the bench at Wembley Stadium last weekend, likely forcing Andre Gray back down to the bench.
Skipper Deeney has scored nine Premier League goals this season, only netting more in the 2015-16 (13) and 2016-17 (10) campaigns, and he will be one of the first names on the team sheet.
Watford possible starting lineup:
Foster; Janmaat, Mariappa, Cathcart, Masina; Hughes, Doucoure, Capoue, Pereyra; Deeney, Deulofeu
Arsenal possible starting lineup:
Leno; Mustafi, Koscielny, Monreal; Maitland-Niles, Ramsey, Torreira, Kolasinac; Iwobi, Mkhitaryan; Aubameyang
Head To Head
Watford have lost four of their previous five home games against Arsenal in the Premier League, but they did win their most recent such encounter 2-1 last season.
The Gunners have not lost back-to-back away league matches at Watford since a run of three straight defeats ending in November 1987.
None of the previous 11 Prem encounters between these two sides has ended in a draw, with Arsenal winning nine and Watford claiming victory twice.
We say: Watford 1-1 Arsenal
Watford are locked in a four-team battle for seventh place and Arsenal are in a four-team battle for the two remaining Champions League spots. Both teams may have other competitions to think about - the FA Cup for the Hornets and the Europa League for the Gunners - but the Premier League takes priority on Monday and we are expecting a tight contest.