The midfielder was carried off the pitch on a stretcher during Canada's 6-0 thrashing of nine-men Qatar in Thursday's (06.18.26) World Cup group match, after he was brought down.
Qatar's Assim Omer Madibo was handed a red card for his challenge on Kone, who appeared to suffer a serious leg injury.
Afterwards, Marsh said: "Ismael is such a great kid. He’s so imperfect but that’s part of why you love him.
"He can do great things that nobody else can do, then the next moment he loses concentration.
"He embodies us as a team, it’s a huge loss for us."
Marsch also admitted Kone is a "big part" of Canada's future.
He added: "He’ll be fine, we’ll get him good doctors and get him back but that kid is a big part of our future and everything we do."
The former Watford player waved to fans as he was carried off the pitch.
Elsewhere during the match, Canada's Jonathan David scored a hat-trick to send his nation top of Group B.
Cyle Larin had opened the scoring for Canada in the 16th minute against Qatar, who had Homam El Amin sent off in the first half.
Canada took a 3-0 lead into the break, and Nathan Saliba scored a free-kick in the 63rd minute.
He paid tribute to Kone afterwards, holding up his shirt to the crowd.
Mohammad Al Mannai scored an own goal with 15 minutes to play, and Canada sealed an emphatic win in injury time when David completed his hat-trick.
After the game, Marsch was delighted with his team's performance.
He said: "We wanted to play the kind of football that would electrify the crowd, we wanted to showcase the talent and the mentality we have.
"There will be 40 million Canadians who will claim they were in the stadium today.
"These 55,000 were lucky. What a performance from our team.
The best resource of this national team program is the players. They embody everything that is great about this country. They are incredibly kind, generous and giving to each other. They are great talents and competitors. Coming here, my job was to elevate them in every potential. It's a great group of kids."
