The 23-year-old central midfielder came off worst following a collision with Steven Gerrard in Saturday's 1-0 defeat at Anfield.
The defeat means Reading are yet to win a Premier League game in seven attempts this season, leaving Brian McDermott's men one place off the bottom of the table.
To make matters worse, Karacan appears to have sustained a knee ligament injury, with the Turkish ace set to undergo a scan later this week to determine the extent of the damage.
A deflated Karacan explained: "It was a fifty-fifty challenge. I did the same thing five years ago for the reserves and it feels pretty similar to that.
"I've done the medial ligaments before so I knew when I did it that it wasn't great. I was able to walk so I thought I would give it a go, but it was too loose so I had to come off.
"It's one of those things but I can't get it scanned for a couple of days because it's too swollen so I'll know more a bit later.
"It was a fair challenge, you go for them all the time, but I got a bit unlucky so it's just one of those things."
Karacan only recently returned from breaking his ankle towards the end of last season and he says Saturday's incident is not the first time he has damaged knee ligaments either.
"Last time I tore the ligaments so was out for a couple of months," he said. "But it was at the end of the season so I had the summer break and pre-season.
"I'm hoping this time it won't be longer than a month but you can't put a timescale on it yet."
And he added: "After coming back from however long, four or five months, after my ankle, it's gutting. The worst runs through your mind, you don't know how bad it is and when you are going to kick a ball again.
"Every day I eat, sleep and breathe football so to have that taken away from you is the worst thing in the world, but after I find out more I will judge the timescale.
"It is frustrating because you want to play against the best players in the world and Steven Gerrard is one of them."
Reading are now facing a make-or-break period over the next month as they bid to climb the Premier League table.
McDermott's men host Fulham at Madejski Stadium this Saturday (3pm ko) then entertain Arsenal in the Capital One Cup third round on Tuesday, October 30 (7.45pm ko).
But it is the month of November which could be the most defining with clashes against QPR, Norwich City, Wigan Athletic and Aston Villa on the horizon.
And Karacan argued: "We could have nicked something on Saturday. We had a couple of opportunities, we just need that run of the ball which we haven't been getting. We need to look at the positives and how we can stop the opposition creating chances.
"We have a big game at Fulham at home now, we need everyone behind us. One win moves you up the table a couple of places, it's still early doors.
"There's a long way to go, we don't need to press the panic button, we have a great group of lads and we will show that."