Claude Puel says its hard to accept Southampton's exit from the Europa League after conceding late in their 1-1 draw with Hapoel Be'er Sheva on Thursday.
The Saints needed at least a 0-0 draw to progress to the knockout phase of the competition but conceded in the 78th minute when Maor Buzaglo fired home, before Virgil van Dijk gave his side a tiny glimmer of hope with his injury-time equaliser.
After the game, a disappointed Puel said it was just one error that cost his side, before looking forward to the Premier League clash with Middlesbrough at the weekend.
He told the club's official website: "It's a big disappointment. It was a difficult game against a good opponent, who were always dangerous when they recovered the ball, but we had chances during the game.
"Just one mistake, one shot at the end – we lost the ball and it's a goal. It's very hard to accept this situation, and very hard of course for my players. It's a big disappointment for all the squad and the fans also.
He added: "Tonight, all the words are difficult, but this is football. It's a big disappointment, because we gave it our all. It's very hard to be eliminated, but now it's important to have a good reaction from all the team."
The Saints host Boro this weekend and Puel is hoping for a swift response.
He said: "It's important to look forward and come back with a good spirit and come back in the first half of the table and keep the good concentration for the next game in the Premier League.
"It's an opportunity to play quickly. It's a good thing to have this game on Sunday and to have a good reaction."