Claude Puel said it was hard to sum up his emotions after Southampton exited the Europa League following a 1-1 draw with Hapoel Be'er Sheva on Thursday.
A win or a goalless draw at St Mary's would have been enough for Saints to progress to the last 32.
But they were largely lacklustre and, after falling behind to Maor Buzaglo's 78th-minute strike, could only grab a late equaliser through Virgil van Dijk.
"It's a big disappointment," said Saints boss Puel. "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.
"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."
To add to Saints' disappointment, they lost Charlie Austin to injury in the first half.
The striker went off holding his shoulder, and Puel said: "I don't know how long he will stay out, but for the moment he is injured."