Thierry Henry was pleased to see his Monaco side display their battling qualities as they edged into the semi-finals of the Coupe de la Ligue.
Monaco fell behind at Stade Louis II on Wednesday as Rennes netted on the half-hour mark, but the home side pulled level through Rony Lopes shortly after the break.
The game finished 1-1 and, in the ensuing penalty shoot-out, Monaco found themselves at a disadvantage when Youri Tielemans failed with their second kick.
But goalkeeper Loic Badiashile proved the hero - saving three Rennes efforts before dispatching the winning kick himself as Monaco prevailed 8-7 and advanced to a last four that will be missing Paris Saint-Germain and Lyon after their shock exits at the hands of Guingamp and Strasbourg respectively.
"It was difficult for both teams. Rennes had the opportunity to win and so did we. Loic's match was extraordinary and not just during the penalty session," Henry said.
"It's been a long time since we had so few opportunities in a game. For a long time we couldn't find players in the spaces and the opportunity to play between the lines.
"What particularly pleased me tonight is the attitude of the players who have always tried to improve.
"We conceded a goal and we reacted. I liked it, and it's very important. The fans saw a team who fought.
"It is always a satisfaction as a coach to see on the pitch what we have been working on in training. We will not give up. There has been work done, and work that remains to be done."
Monaco return to Ligue 1 action and their battle to avoid relegation when they travel to Marseille on Sunday.