The table is extraordinarily tight, with only five points separating 11th-placed Watford and Stoke in 19th.
And Carvalhal reckons the logjam at the bottom shows how much work there is still to do.
“I think it's normal for this competition to be close because there are not big differences between the teams," he said.
“Some clubs started the season very well and then lost some points. Other teams, like us, did not start so well but have picked up some more points recently.
“The season is a marathon, and at the end of the marathon the worst team will be last and the best team will be first.
“We are fighting to be one of the teams who stay out of the last three positions.
“We are fighting very hard but there's still a long way to run."