Paris Saint-Germain’s hopes of a domestic treble were over after a surprise 2-1 home defeat by Montpellier in the French Cup on Wednesday. PSG had scored 15 goals in the four previous games, but coach Laurent Blanc’s decision not to start with regulars Zlatan Ibrahimovic, midfielder Thiago Motta and goalkeeper Salvatore Sirigu backfired against an inspired Montpellier team that advanced to the last 16 of the cup. Backup goalkeeper Nicolas Douchez was at fault for the first goal as he failed to come for a cross and defender Daniel Congre headed home in the 20th minute. After PSG went out at the quarterfinal stage of both Cup competitions last season, the club’s Qatari owners made winning them a priority this time. “We’ve played really well during the month of January, but tonight we didn’t and that annoyed me,” Blanc said. “We didn’t do what we had to do and we were punished by a Montpellier side that took their chances very, very well.” Uruguay forward Edinson Cavani equalized for PSG 10 minutes later, but slack marking allowed Colombian forward Victor Hugo Montano to head a 69th-minute winner for a team languishing in 16th place in the league. “It’s an upset, I hope we won’t be too tired against Nice on Saturday, but it’s extraordinary to win here in Paris,” Montpellier owner Louis Nicollin said. “It was impossible. They’d scored five at the weekend (against Nantes).” Cavani scored his 20th goal of the season with a tap-in from left back Lucas Digne’s cross, but he somehow missed an open goal moments later. Javier Pastore’s shot was then saved by goalie Laurent Pionnier in the 55th as PSG squandered chances.