Madrid went ahead through Karim Benzema's deflected shot the 23rd minute, before Soler equalised from the spot 12 minutes later. Thibaut Courtois had saved his initial effort and Yunus Musah scored the rebound before VAR spotted players from both sides encroaching and the penalty had to be retaken.
Valencia were ahead by half-time, after Varane deflected in his own goal, and could have increased their lead when Courtois tipped Kang-in Lee's shot onto the post. Soler scored his second penalty after Marcelo fouled Maxi Gomez and grabbed a third to make sure of the win when Sergio Ramos handled inside the box.
Despite trailing at the break, Real Madrid played pretty well in a first half that saw Luka Modric dominate midfield and the team cope without the absent Casemiro. They had more possession, and more shots on goal than their opponents. At that stage, some of the pre-match worries -- especially the selection of Marcelo at left-back -- looked unfounded. All that changed soon enough.
Real Madrid conceded three penalties in a La Liga match for the first time ever. The first, when Lucas Vazquez handled, was perhaps the least egregious. Marcelo's challenge on Gomez for the second was clumsy, and then Ramos' handball was inexplicable. Valencia played their part, but really, Madrid hit the self-destruct button.
The team's recent record at Mestalla is dreadful, and now reads just one win in the last seven league visits. Here, they there were embarrassed by a Valencia team shorn of its best players -- Dani Parejo, Rodrigo Moreno, Ferran Torres, Francis Coquelin, with Geoffrey Kondogbia the latest to go -- in recent months.
Manager rating out of 10
5 -- There were two surprise names in Zinedine Zidane's starting line-up: Marcelo and Isco. Neither player has impressed this season and they were bold selections away at Mestalla. Marcelo looked good early on before fading, but Isco struggled to get involved throughout.
Zidane's substitutions were predictable, throwing on a series of attacking players as the team trailed, but there was no sustained assault on the Valencia goal and no clear idea of what he wanted from the team either. There will be pressure on the coach now.
Player ratings (1-10; 10 = best. Players introduced after 70 minutes get no rating)
GK Thibaut Courtois, 6 -- Beaten three times from the penalty spot although he saved Soler's initial first-half effort and got close to two others. Did really well to get fingertips to Lee's second-half shot.
DF Lucas Vazquez, 5 -- Poor, after doing well at right-back lately. Conceded the penalty that started Valencia's comeback and later missed a good chance to make it 4-2.
DF Raphael Varane, 5 -- Scored an unfortunate own goal. That can happen, but this was Varane's second of the season. Varane is rarely questioned, but he needs his form to improve fast.
DF Sergio Ramos, 5 -- Badly beaten by Lee early in the second half and then committed a bizarre, unnecessary handball to gift Valencia the penalty that put them 4-1 up.
DF Marcelo, 5 -- Looked better at first than he has looked so far this season, up against the pacey Musah, but that didn't last. Another guilty party, giving away a penalty at a crucial time in the match.
MF Luka Modric, 7 -- Probably Madrid's best player. Has an unmatched ability to receive the ball in midfield, escape challenges and find space. One gorgeous pass to play in Marco Asensio in the second half.
MF Isco, 4 -- Very quiet again. One cross just over the head of Asensio was his only contribution of note. Keeps passing up the opportunities he's given.
FW Karim Benzema, 7 -- Five goals in four games now. Got some luck with a deflection, but it was still a powerful shot fired in from the edge of the box through a crowd of defenders. Limped off with what looked like a groin injury.
FW Rodrygo, 6 -- Replaced Asensio but was quiet.
MF Martin Odegaard, 6 -- Thrown on to try to spark a comeback. A nice pass for Vazquez to shoot over.
MF Toni Kroos, NR -- Came on for Valverde.
FW Mariano Diaz, NR -- His first appearance of the season. Had one shot wide.
FW Luka Jovic, NR -- Played the last 10 minutes with no impact.