BARCELONA: Cristiano Ronaldo helped Real Madrid prime its attack for its highly anticipated Champions League clash with Manchester United by scoring his 21st career hat trick in a 4-1 home win over Sevilla in the Spanish league on Saturday.  

After a defensive blunder let Karim Benzema open for Madrid 18 minutes in, Ronaldo unleashed an unstoppable strike to double the advantage in the 26th. The former Manchester star then went on to find the back of the net twice more after halftime.

Ronaldo did his best to make amends for his own goal that cost Madrid a loss at Granada in the last round with his 22nd, 23rd and 24th goals in the league this season. Only Barcelona's Lionel Messi, with 34, has scored more.

Madrid stayed in third place. It trails Barcelona by 13 points before the leader hosts Getafe on Sunday.

With Madrid's Spanish league title defense all but mathematically impossible, a large share of its silverware hopes this season now rest on its round-of-16 Champions League tie with United starting in the Spanish capital on Wednesday.

''For Madrid every game is special, but on Wednesday we have to be ready to meet the challenge,'' said Madrid defender Pepe, who went on late for his first action since surgery on his right ankle in early January.

''Cristiano is playing well. He is working hard and we need him to keep it up.''

Also, substitute Nelson Valdez scored in stoppage time to give Valencia a 1-0 win at Celta Vigo just three days before its Champions League series with Paris Saint-Germain.

Apparently with the English challengers in mind, Madrid coach Jose Mourinho left Xabi Alonso off his squad and fellow first-choice midfielders Mesut Oezil and Sami Khedira on the bench.

Instead, sparingly used Kaka got his first start since Dec. 4.

Madrid eased in front when Benzema was well positioned to take full advantage of a miscue by Sevilla's defense. Sevilla goalkeeper Antonio ''Beto'' Bastos deflected Ronaldo's low cross off teammate Fernando Navarro, and the ball fell for the France striker to nudge it over the goal-line.

Madrid kept the pressure on and Ronaldo made it 2-0 when he shimmied around Sevilla midfielder Hedwiges Maduro, put the ball on his left foot, and let loose a dipping shot from beyond the area that struck the net just inside the far upright.

Barely 30 seconds into the second half, Ronaldo made Sevilla defender Federico Fazio pay dearly for his sluggish response to reach a pass as he beat him to the ball and fired under the helpless Beto.

Ronaldo wasn't done and finished off a counterattack in the 59th that he had started from near his own area, racing forward to tap in Gonzalo Higuain's cross.

Four minutes after recording his 20th hat trick for Madrid, he scored one for Manchester, Ronaldo was substituted to a standing ovation by the Santiago Bernabeu crowd.

Higuain left Madrid with 10 men from the 66th after he picked up his second yellow card. Maduro followed suit for Sevilla in the 81st.

Manu del Moral got Sevilla's consolation goal in the 87th.

Earlier, Celta was clinging to a scoreless draw before Valdez went on in the 89th. Three minutes later the Paraguay striker maneuvered free to head Joao Pereira's cross into the net at the far post and claim Valencia's dramatic victory.

Valencia, which moved into fifth place, hosts Paris Saint-Germain on Tuesday in the first leg of their round-of-16 Champions League tie.

''The game was heading to a 0-0 draw, it was a cruel result for Celta,'' said Valencia coach Ernesto Valverde. ''In the second half the game tilted more and more to our favor, and we were just lacking that last pass.''

Elsewhere, Francisco ''Isco'' Alarcon netted two times to lead Malaga back to a 2-1 victory at Levante, while defender Geromel also scored after 90 minutes to give Mallorca a 1-1 draw with Osasuna and salvage coach Gregorio Manzano's return.

Malaga's second consecutive away win kept it in fourth place and in control of Spain's final Champions League spot thanks to the two-goal effort from the 20-year-old Isco, who made his international debut for Spain on Wednesday.

Manzano began his third stint with Mallorca on Tuesday when he replaced the fired Joaquin Caparros. Mallorca is in second-to-last place after just one win in its last 18 games.    Granada kept Deportivo La Coruna in last place with a 3-0 win at Riazor.

Also on Sunday, second-place Atletico Madrid visits crosstown rival Rayo Vallecano nine points behind Barcelona. Real Zaragoza hosts Real Sociedad, and Espanyol is at Athletic Bilbao. Valladolid visits Real Betis on Monday.