Portuguese manager Marco Silva has already made five additions to his squad since replacing Walter Mazzarri in the shape of Tom Cleverley (Everton), Will Hughes (Derby County) Daniel Bachmann (Stoke) Nathaniel Chalobah (Chelsea) and Kiko Femenia (Alaves). Furthermore, the Hornets are also expected to complete the signing of Brazil U20 forward Richarlison from Fluminense to bolster their attack.
Silva has now earmarked the signing of a left-back to provide competition for 33-year-old Jose Holebas as a priority target as he continues the revamp of his squad.
Arsenal's out-of-favour full-back Kieran Gibbs has been touted as a candidate in recent days and IBTimes UK understand that the Hornets have also approached Liverpool over a possible move for Moreno.
The Spanish left-back was displaced at Liverpool by James Milner last term but Silva is eager to lure him to Watford due to his speed and ability going forward.
The Hornets, however, may struggle to convince Liverpool to cash in on the player as the Reds are looking to recoup the investment they made to sign him in 2014, when they paid an initial £12m fee to snare him from Sevilla.
Earlier this week Moreno already suggested that he may need to leave Anfield this summer after Jurgen Klopp brought Andrew Robertson from Hull City to bolster the left-back position ahead of the coming season.
"Yes. It is clear [until 31 August everything can happen]. Robertson has arrived, we are now three left-backs. Milner is currently injured. There are many turnarounds in the football. I have to fight and see what happen in the new season," Moreno said to Cadena Ser this week after making a rare starting appearance in the pre-season 3-0 victory over Bayern Munich.
"Many things have being said [about my future] but right now I am fighting for my position in the left-back. It's true that last season I did not play as much as I wanted but football is like that. One day you are up, another day you are down. This year we start from scratch again. I have to work from the first minute and let's see what happens during the transfer window,"
Yet, following that game against Bayern, Klopp also suggested that he may even give the Spaniard a chance to resurrect his Liverpool career in the coming season.
"If he plays like he did today then yeah (he has a chance of playing)," Klopp said in the press conference. "It was a really good game from Alberto, that's why we kept him on, because every second he was playing better, he was more present."
"He's really fit but he's had a little problem with his thigh since the day before yesterday. But we had a test with him this morning and he really played well. The players decide themselves how many games they play."