Guidolin's men have scored just once in their past four games – three of which have been losses – to slip to 13th in the Serie A.
Di Natale tops their goalscoring with four, but Guidolin said his side needed to ease the load on the 36-year-old.
"In the last few games we have only scored one goal. Di Natale can't do everything himself," Guidolin said.
"This league is tough, and our current league position shows that."
Guidolin also spoke about the abuse of Serbian goalkeeper Zeljko Brkic during his team's 1-0 loss to Juventus on Sunday.
Juventus have been fined €5,000 after children repeatedly insulted the shot-stopper and Guidolin described the abuse as 'troublesome'.
"I wanted to say something right after the game because it bothered me but I didn't want to put any oil on the fire and I decided to stay quiet," he said.
"For a club such as Juventus where everything is beautiful, in particular where the stadium gives you the idea that you are not in Italy, it is really troublesome to hear those words every time the goalkeeper puts the ball into play."
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