Morata sends Real top
Real Madrid took advantage of Atletico Madrid's first defeat of the season at Sevilla to move to the top of La Liga as Alvaro Morata struck a late winner to secure a 2-1 win over Athletic Bilbao on Sunday.
Steven N'Zonzi struck Sevilla's winner 17 minutes from time to seal a 1-0 win at a soggy Sanchez Pizjuan.
Real lead Sevilla by a point and Barcelona and Villarreal by two at the top of the table.
Atletico, who started the weekend top, slip to fifth, three points back on their city rivals.
"We are not going to have easy matches and we will have to fight until the end," said Real boss Zinedine Zidane.
"That is the message I transmit to my players and today we believed and didn't give up in the difficult moments."
Madrid couldn't have hoped for a better start when Enric Saborit's slip allowed Isco to tee up Karim Benzema for a simple finish after just seven minutes.
However, Real's defensive deficiencies surfaced once more when Athletic levelled in scrappy fashion as Javier Eraso's tenacity won the ball inside the Madrid box for Merino to slot home.
Cristiano Ronaldo suffered another off night in front of goal and was even jeered by the Bernabeu crowd when shot straight at Gorka Iraizoz with Isco and Benzema begging for a cut-back for a tap in.
Real were handed a lifeline when Inaki Williams blazed over with just Keylor Navas to beat early in the second period.
Zidane turned to Morata off the bench 15 minutes from time.
And the Spanish international ensured Real didn't drop points at home for a third consecutive La Liga game as he bundled Gareth Bale's low cross home at the near post.
Athletic still had the chance to snatch a point, but once again Williams misfired when clean through on goal to the relief of the Bernabeu.
And Real should have had a third with the last action of the match when Ronaldo selfishly went for goal and was again denied by Iraizoz to the fury of the supporting Toni Kroos.
Atletico were also left to rue not taking their chances in the first-half as on-loan Atletico striker Luciano Vietto came back to haunt his parent club.
Kevin Gameiro shot straight at Sergio Rico and Angel Correa wastefully wide before the break.
The in-form Samir Nasri smashed against the post before Jan Oblak made a remarkable save to prevent Vitolo opening the scoring on the volley from point-blank range as Sevilla started the second-half strongly.
Vietto endured a woeful debut campaign at Atletico last season after a 20-million-euro ($21.8 million) move from Villarreal and was used as a makeweight in the deal that brought Gameiro to Atletico in the summer.
However, he clipped a fine ball over an uncharacteristically static Atletico defence for N'Zonzi to run through and slot coolly past Oblak.