Here are five talking points from the weekend's action in La Liga.
The Argentine teenager has been out of action after he tore a thigh muscle during the Champions League match against Chelsea
Arsenal, Olympique Lyon and Villarreal try to venture into the unknown this week when the second legs of the Champions League quarter-finals take place.
Last season's Champions League flops, Manchester United and Celtic will seek a flying start when they meet in the Group F tie at Old Trafford.
The 21-year-old is the latest youngster to join Atletico who have also brought in Argentine forward Luciano Vietto from Villarreal since the end of last season.
Twice former winners Benfica came from behind to beat the English side 2-1 to reach the last 16 of the tournament.\nA round-up of Wednesday's matches.
Leading striker Samuel Eto'o will also miss the Champions League Group C match at Udinese because of a bruised ankle.
Barcelona striker Samuel Eto'o finished with 26 goals as he scored in his side's 3-1 defeat at Athletic Bilbao.
Zinedine Zidane, Walter Samuel and Michel Salgado will sit out during the match against Real Sociedad
Manchester United visit Lille in the Champions League on Wednesday with manager Alex Ferguson under extreme pressure following Saturday's 4-1 thrashing at Middlesbrough.
Espanyol secured a commanding lead in their King's Cup quarter-final tie against Sevilla when Felipe Caicedo, Sergio Garcia, with a penalty, and Lucas Vazquez scored in a 3-1 first-leg home win on Thursday.
Barcelona beat AC Milan on a 1-0 aggregate, after the second leg semi-final ended goalless.
Arsenal beat Villarreal on a 1-0 aggregate after the second leg semi-final ended goalless.
The Manchester United striker was handed a two-match ban following his sending-off in the Champions League match at Villarreal last week.
Inter Milan coach Roberto Mancini has warned his players against relying on defence when they play Ajax Amsterdam for a place in the quarter-finals on Tuesday.
The Spanish champions went through on 3-2 aggregate after the second leg pre-quarter-final ended 1-1. Juventus and Villarreal also made it to the quarter-finals.
Barcelona beat local rivals Espanyol 2-0 in the Catalan derby on Saturday to maintain their 10 point lead at the top of La Liga, while Real Madrid scraped a 3-2 win against bottom side Huesca on Sunday.
Villarreal went through to the group stage on a 4-2 aggregate crashing Everton's Champions League.
Barcelona earned a valuable 2-1 away win at Chelsea, with the home side playing most of the match with only 10 men.
Inter Milan staged a fierce second-half fightback to draw 2-2 at Ajax Amsterdam.
Werder Bremen scored two late goals to snatch a 3-2 win at home to Juventus and give themselves a chance of making the Champions League quarter-finals.
Striker Aduriz opened the scoring in the sixth minute at the San Mames with a trademark header before midfielder Garcia, who joined from Atletico Madrid last month, nodded in a second in the 24th minute.
Ronaldo was named in the Real Madrid squad for Saturday's home league match against Espanyol after a month out with a calf strain.
Real Madrid striker Ronaldo suffered a recurrence of a calf injury during the 0-0 draw at Villarreal on Sunday.
Manchester United took over at the top of the Premier League while Barcelona's Argentine forward Lionel Messi could be out for up to two months with a knee injury and rampant Bayern Munich extended their perfect start to seven league wins.
Villarreal's Brazilian midfielder Marcos Senna tested positive for two banned substances.
News of all that transpired on and off the football field
Real Madrid wasted a chance to keep the pressure on the top two in La Liga with a 2-2 draw away to Osasuna where Sergio Ramos was sent off and record signing Gareth Bale substituted.
Barca's second-half stamina key to their massive lead in the standings this season
Atletico Madrid's faint hopes of chasing down runaway Liga leaders Barcelona suffered a fresh blow on Saturday as they were held to a 1-1 draw at home to Girona, meaning they could fall 11 points behind the Catalans by the end of the weekend.
An impudent individual goal from Philippe Coutinho steered Liverpool comfortably into the quarter-finals of the Europa League on Thursday after a 1-1 draw at bitter rivals Manchester United completed a 3-1 aggregate win.
