Klopp was initially planning to take James Milner off for Alex Oxlade-Chamberlain with a little over 10 minutes remaining in the match, but Coutinho then jogged to the touchline and asked to be withdrawn himself.
The match was Coutinho's first start of the season for Liverpool, and despite seeing it come to a premature end Klopp was pleased with the Brazilian's performance.
"He did well. He needs rhythm, that's normal. I didn't want to change him at the end, that's why it looked a bit confused as we brought the subs on," he told reporters.
"I asked him to stand up, but then obviously when we got the drinks in this little interruption we saw. It was only a cramp but it was maybe better to stop and we had to change this."
Liverpool have now taken just one point from their last two league games, leaving them eighth in the Premier League table.