Swansea still suffering from derby defeat
Michael Laudrup's men currently sit 13th, just one point worse off than at this stage last year, but Wieghorst feels the 1-0 defeat to local rivals Cardiff at the beginning of November has contributed to a negative impression of the club's Premier League performance.
Swansea could climb into the top half of the league if they end a three-match winless run with victory over Fulham on Saturday and the Dane believes there is no time for excuses.
"It is not an excuse - we still have to win games - but some people have had their views coloured by the fact that we lost at Cardiff," he told the South Wales Evening Post.
"That was a massive disappointment to everyone. We did well in the first half at Cardiff but in the second half we were poor.
"That's had an influence on how people are looking at the whole season.
"We want to put that right the next time we play Cardiff, but right now we can't do anything about it."
Swansea have won both of their fixtures at Craven Cottage since gaining promotion to the top flight in 2011.