Luis Suarez's flicked finish early in the first half looked to be enough to give Atletico a crucial win that would have put them eight points clear of their opponents, with a game in hand.
European football matchday: City hope to close in on Premier League title in Manchester derby; Atletico face Real in Madrid derby
Manchester City can virtually ensure a procession to the title in the final weeks of the season by beating Manchester United while Atlético Madrid will be aiming to leave its city rival eight points adrift in third place with a victory
Simeone and Zidane have previously locked horns in the Madrid derby on 13 occasions, 12 times as managers of their respective sides, and once as players.
Lionel Messi set up both goals in Pamplona as Jordi Alba hammered home in the first half before the 18-year-old Ilaix Moriba came off the bench to curl in an impressive shot late in the second.
European football weekend: Massive Madrid derby, 'Klassiker' in Germany, Inter look to extend Serie A lead
LaLiga leaders Atletico Madrid have an opportunity to deal a hammer blow to their city rivals' attempts to retain their league title as they host Real Madrid in a potentially decisive Madrid derby.
LaLiga: Barcelona ditching Luis Suarez was a 'huge mistake', says former Atletico Madrid striker Diego Forlan
Forlan goes back a long way with Luis Suarez, to 2007 when he set up Suarez's first goal for Uruguay and to 2013, when Suarez set up Forlan's last.
Barcelona are coming off their first season without a trophy since 2007-08 and have a debt of more than 1.1 billion euros, largely because of the coronavirus crisis.
Premier League: Jose Mourinho says Real Madrid to blame for Gareth Bale's slow start to life at Tottenham
The Wales star's second spell at the north London club looked like it might become a disappointment after two years of largely being sidelined by Spanish giants Real.
The result ends Real Madrid's run of five consecutive wins while Portu's brilliant header for Real Sociedad early in the second half was also the first goal conceded by the reigning champions in five games.
Several media reports have suggested that an agreement with Neymar has already been reached.
Champions League: Ferland Mendy's late strike helps Real Madrid beat Atalanta in Round of 16 first leg
Madrid have the advantage going into the second leg having missed out on the quarter-finals for the last two seasons.
There is a vast gap between 13-time European champion Real Madrid and Atalanta, who are making only their second appearance in the competition.
For most of this century, it has been a question of when, not if, a generational talent moves to Spain but now there are no guarantees.
LaLiga: Real Madrid move close to top with win over Valladolid; Atletico suffer surprise loss against Levante
Real Madrid's victory at the Jose Zorilla Stadium was their fourth in a row, three of those coming with clean sheets, which suggests a return to form for a defence that all but clinched them the title last season.
Madrid might cope without Benzema against Valladolid but his absence for the trip to Bergamo in the first leg of the Champions League last 16 on Wednesday would be a huge blow.
Modric is joint third top scorer at the club and fifth for assists, even though by his own admission his contribution is never truly reflected by those measurements.
Bundesliga chief executive Christian Seifert slams 'cash-burning' European clubs for chasing Super League
UEFA is pursuing an expanded 36-team format that gives more guaranteed games and revenue that elite clubs have demanded, while also retaining a path to qualifying for teams from all of Europe's top-tier leagues
Jose Mourinho's team have been involved in 22 Premier League matches following Bale's return to the north London club but the 31-year-old has started just two of those.
David Alaba's announcement came two days after Bayern signed French defender Dayot Upamecano from Leipzig on a five-year contract.
The victory moved Real Madrid three points in front of third-place Barcelona, which routed Alavés 5-1 at home on Saturday.