The veteran striker leads the Spanish scoring charts this season and comes into the match after Zinedine Zidane's side lost ground in the title race when it was held to a 1-1 draw by Elche in midweek.
Atletico, however, defeated Getafe 1-0 and has a two-point lead as well as two games in hand.
Since the arrival of 46-year-old Argentine coach Eduardo Coudet, Celta has soared from the edge of the relegation zone to eighth in the table.
That turnaround has been achieved on the back of a run of six wins, a draw and just one loss in its past eight games.
Celta is just two points behind Barcelona.
Aspas, 33, has been instrumental for Celta with nine goals in La Liga this season.
He even leads the top scorers charts with one more goal than Real's Karim Benzema and two ahead of even Barcelona superstar Lionel Messi.
"Aspas is spectacular, he's also an international," Zidane said of a player who once spent two seasons on Liverpool's books.
"He has always proved it, he is very good. He's the kind of player who makes a difference. He's a key player for them."
Atletico's victory in midweek came in coach Diego Simeone's 500th match in charge.
It faces 13th-placed Alaves on Monday (AEDT) looking for a fourth consecutive win.
Key will be Luis Suarez, who grabbed the winner against Getafe, taking his goals total to eight for the season.
Third-placed Real Sociedad, six points off the top, hosts Osasuna on Monday (AEDT).
Barcelona, 10 points behind Atletico, ended a mediocre 2020 on Wednesday (AEDT) with a 1-1 draw against Eibar.
It starts 2021 on Monday (AEDT) with a trip to bottom club Huesca.
Messi, who missed the game with Eibar with a right ankle injury, enters the new year with just six months left on his contract and more questions than before over his future plans.