Real Madrid coach Jose Mourinho has conceded it would now be "practically impossible" for his side to win the Primera Division title.
A late strike from Miguel De las Cuevas saw Sporting claim a 1-0 win at the Bernabeu on Saturday night and bring to an end Mourinho's remarkable record of not having lost a home league game as a coach in over nine years.
The loss also ended Madrid's perfect record at the Bernabeu this season, and allowed Barcelona to stretch their lead to eight points as they defeated Villarreal 1-0 at El Madrigal.
Mourinho, while refusing to give up the fight, admits his side's title hopes are all but sunk with only eight games remaining after this weekend.
When asked if the league had been lost on Saturday, Mourinho said: "Until the mathematics say otherwise then no, but looking at things pragmatically and objectively, if today Barca increase their lead to eight points you could say it's practically impossible."
Madrid defender Sergio Ramos added in AS: "A large part of the league has gone away from us. There are very few points left.
"We can't reproach the team for anything. Unfortunately the ball did not go in today. It's very sad to lose with so many chances."
The Spanish giants welcomed back Gonzalo Higuain after over four months out due to a back injury that required surgery and the Argentina international was introduced a second-half substitute.
However, Mourinho was still missing a number of key players for the match with Cristiano Ronaldo, Karim Benzema, Xabi Alonso, Kaka and Marcelo absent through a mixture of injury and suspension.
Without those players Madrid struggled to create anything of note during the first half and, although they laid siege to the Sporting goal in the final 10 minutes, they could find no way through.
Madrid must now lift themselves ahead of Tuesday's Champions League quarter-final first leg against Tottenham, with question marks still surrounding whether Ronaldo will be fit to play.
At Friday's pre-match press conference Mourinho suggested none of Ronaldo, Benzema or Marcelo would be available until next weekend's league game against Athletic Bilbao.
However, when asked following Saturday night's game what chance Ronaldo had of making the squad for the Spurs game, Mourinho said: "If he has a chance, it's because he and his coach are taking a risk.
"Because the information from the medical department is that he can't play, that he can only play in the game in Bilbao.
"But if the two of us and only the two of us decide that he's going to play then the risk is mine and his.
"Tomorrow I will talk with the injured players and decide if we will risk them."
Saturday night's defeat saw the end of Mourinho's 150-match unbeaten home league run as coach of Porto, Chelsea, Inter Milan and now Madrid.
The Portuguese said: "Our opponents defended, defended and defended. They had one chance and they scored one goal. I praised them because they fought a lot and they fought to try to have luck on their side.
"We had four, five, six chances to score and we couldn't. That's football and tomorrow's another day."
He added: "We played without the team's most creative players. We lacked creativity. We had to try a different style, more direct with long balls in the air, and we had more opportunities.
"If I had wanted to draw the game 0-0 from the start I would have done so. But a draw was a bad result. Against Tottenham on Tuesday, it won't be. If we draw at home, it would not be a drama because we will have the return to play in London."