Smith, best known for directing "Clerks", had recently revealed that he had suffered a massive heart attack. Smith is currently recovering in California's Glendale Memorial Hospital.
Pratt was among the celebrities who tweeted their support to Smith. He posted, "Kevin we don't know each other too good but I have loved you since Clerks and Im praying my ass off for you cause I believe in the healing power of prayer. Can you please pray with me people?"
The actor was slammed on Twitter on with some users arguing against the thoughts and prayers approach in response to recent mass shootings that have taken place in the United States.
The argument goes that thoughts and prayers are not helpful and that action is needed to effect change. Many fans tweeted that "prayer does nothing" and "Doctors and nurses save lives not prayer".
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"So I just read Chris Pratt's tweet to Kevin Smith saying he would pray for him & made the mistake of reading the comments, many of which go off on Chris for saying he'd pray. I think people misunderstand the backlash against 'thoughts & prayers'," Gunn tweeted
"There is nothing wrong with sending someone positive thoughts & prayers. But when this is coupled with inaction when action will benefit the situation, it's empty," he added.
Gunn, who has been very vocal about taking action against gun violence in the United States in the past, later specifically addressed the issue.
"But no one expects Chris Pratt to shoulder doctors out of the way and perform heart surgery on Kevin Smith. Nor does Kevin need Chris to pay his medical bills. So I think his prayers are appreciated, and about all he can do..." he added.
The director also said that he would "gratefully" accept prayers in the future if he becomes sick.