Coleman was rushed straight to hospital after being carried from the pitch on a stretcher following Neil Taylor's ugly challenge during Friday night's 0-0 World Cup qualifier draw with Wales.
The damage to the 28-year-old Everton full-back's leg was so gruesome that television bosses decided not to show replays of the incident.
Striker Long comforted his team-mate on the pitch and is confident that he will return to his best after what promises to be a lengthy lay-off.
He said: "It's not nice. I was trying to comfort him on the pitch. He's loved by everyone, he's a big player and he will be a big loss.
"He was in a lot of pain. It's a bad injury, so I tried to settle him and relax him. It's not nice to see that happen to anybody, but I think everybody loves Seamus and it's hard to see when he goes down like that.
"I'm sure he will come back fitter and stronger."
Aston Villa's Taylor, who himself spent six months on the sidelines after breaking an ankle in 2012, was instantly dismissed by Italian referee Nicola Rizzoli and Wales boss Chris Coleman later revealed he was "devastated" at the outcome.
Long said: "I think he has got it done to him before, so I suppose he went in worried about the challenge. He caught him high and I think he was in tears afterwards. He knows the pain Seamus was in because, as I said, he's been there before.
"It was a horrible challenge and there is no defending it, but I don't think he meant to do it."
Coleman's misfortune struck just seconds after fellow defender John O'Shea escaped serious injury after being caught by a similarly forceful tackle from Wales star Gareth Bale.
The Real Madrid front man escaped with a booking - he will miss June's trip to Serbia as a result - and Long admitted he might have been fortunate after O'Shea was left needing stitches to repair the wound to his shin.
Read the full article on eurosport.co.uk: Coleman will come back fitter and stronger from leg break, says Long