The 26-year-old, who joined the Reds from Celta Vigo over the summer, has been limited to a handful of appearances in recent weeks following the return of Luis Suarez from a 10-match ban for biting Chelsea's Branislav Ivanovic.
Aspas has now voiced his concerns at being a bit-part player at Anfield.
"I'm finding it hard to be a sub at Liverpool having started games in the past few years," he told the Daily Mail.
"When I left Celta Vigo I was aware that to start for Liverpool wasn't going to be easy, and now the team is winning and we are among the leaders in the Premier League, it's much harder to get a game."
Aspas is yet to score in six appearances for Liverpool this season.