The Hornets' official site confirmed the news, revealing the combative midfielder has joined the club on a four-and-a-half-year deal. Details of the fee paid were undisclosed.
Suarez will now be reunited with manager Quique Sanchez Flores, who once worked with him during his earlier spell with Atletico Madrid, per the report.
Suarez posted a welcome to the Watford fans, expressing his hope for success via the club's official account:
Watford FC @WatfordFC
SUÁREZ SIGNS: Here's a message from Mario! The full interview is available on Hornets PlayerHD! #watfordfc https://t.co/lVYTmFu1Pu2016-1-30 19:08:01
The player also took to Twitter to show his gratitude to Fiorentina supporters, and to also extend his promise to work hard for his new team:
Mario Suárez @MarioSuarez4
I'm officially signing for @WatfordFC. Thank you @acffiorentina and their fans for the support. I will give my all in the @premierleague2016-1-30 19:20:58
The 28-year-old midfielder left Atleti for Serie A during the summer of 2015 but failed to establish himself as a regular with La Viola. Per WhoScored.com, he was mainly used in the UEFA Europa League, where he made three starts.
Those starts were quite impressive, however:
Mario Suárez: Only 1 player to start more than 1 Europa League match this season has better pass success than @MarioSuarez4 (93.6%)2016-1-5 13:00:28
Suarez was a bit of a late bloomer, but he flourished in Spain under manager Diego Simeone, who made full use of his tenacity and impressive defensive range. The midfielder is an excellent ball winner who will run for days, and he also has the technical ability to thrive in possession.
He lost his spot as a regular starter to Tiago Mendes and Gabi in 2014, which is why he made the switch to Fiorentina. But in Florence, Milan Badelj and Matias Vecino have thrived as the central duo, and manager Paulo Sousa has been unwilling to tinker too much with his squad, preferring to keep their strong run going.
Per Football Italia, this understandably led to a lot of transfer speculation surrounding Suarez, and it now seems his search for regular playing time has led him to a new club.
As you can see in the video below, fans should have some cause to be excited about this signing:
Suarez may need some time to find his best form, as he hasn't played that much in the last few months, but he should be able to make strong contributions for his new club before long. His biggest strengths―physical attributes and vision―are universal and should translate to any league, so his transition shouldn't be too difficult.
Suarez was a very underrated part of Atletico's title-winning side in 2013-14, and while he may not be the most polished midfielder, his high work rate and willingness to get his hands dirty will make him a fan favourite before long.