Mallorca have 37 points from 21 games, one ahead of Sevilla, after the Andalusians suffered a miserable night at Real Zaragoza, losing 2-1 and finishing the game with nine men.
The top three, leaders Barcelona, Real Madrid and Valencia all played on Saturday.
Mallorca's Portuguese defender Nunes rose highest to meet a free-kick in the 82nd minute, making it 10 wins from 10 for Mallorca at their Ono Estadi.
"I'm very proud of the team for their conduct, their behaviour and the way they perform on the pitch," Mallorca coach Gregorio Manzano told reporters.
"It's important to keep talking about football and not about what's going on off the pitch," he added. The club are in talks with creditors to try to avoid going into administration.
Sevilla rested players with one eye on Wednesday's King's Cup semi-final second leg away to Getafe, but fell behind when Matteo Contini scored from a scramble at a corner in the 31st minute.
Spain striker Negredo's night went from bad to worse when he kicked Contini as the two tussled for the ball and was shown a straight red card in the 81st minute. His team mate Marius Stankevicius soon followed for a professional foul.
