The Spaniard was signed for around £7 million last summer from Celta Vigo and was given the chance to impress immediately at Anfield as Luis Suarez missed the first five games through suspension.
However Aspas failed to make his mark and eventually scored just one goal - a strike against Oldham Athletic in the FA Cup third round in January.
The striker's most telling contribution in the Premier League was a dreadful corner kick that saw him senselessly pass to a Willian as the Reds searched an equaliser late on in their crucial 2-0 reverse against Chelsea in April.
Following his loan switch back to La Liga, Aspas accepted that his stay at Anfield was an unsuccessful one.
Speaking to Sevilla's official website, he said: “It was a bad season personally, where I didn’t play as much as I wanted."
“I’m happy to come [to Sevilla]. The club put a lot of effort into getting us here.When we knew of the interest of the club, both my agent and I made a lot of effort to come here.”
Aspas featured just 14 times last term as the Reds narrowly missed out on their first league title for 24 years, and his Anfield career appears to be all but over despite the £75 million sale of Suarez to Barcelona.
Brendan Rodgers is reportedly closing in on Queens Park Rangers striker Loic Remy, although a deal for Swansea City's Wilfried Bony appears unlikely at this stage.
The Reds have so far spent around £60 million following the arrivals of Lazar Markovic, Adam Lallana, Rickie Lambert and Emre Can, and the spending could be set to rocket with deals for Remy, Dejan Lovren and Divock Origi all reportedly close to completion.
Meanwhile, Liverpool, who begin their new campaign with a visit of Southampton on August 17, have landed in the USA where they continue their pre-season preparations with games against AC Milan, Olympiacos and Manchester City.