Renner, who plays Hawkeye in several Marvel properties, was injured at home on Saturday (31 December) while trying to get rid of snow around his Nevada property.
According to US reports, Renner accidentally ran over one of his legs, leading to blood loss. The actor received immediate assistance from two of his neighbours, one of whom is a doctor who applied a tourniquet to his injured limb.
Ruffalo, who has starred across Renner in the Avengers films as Hulk, shared a public message for his castmate and friend on social media on Monday (2 January).
“Prayers up for our brother @jeremyrenner on a full and speedy recovery,” he wrote, alongside a news report of Renner’s accident. “Please send healing goodness his way.”
Since news of Renner’s injuries broke, fellow celebrities and friends have shared well wishes and positivity.
“My heart is with Jeremy Renner,” filmmaker James Gunn tweeted, next to the prayer hands emoji.
“My God,” Frozen star Josh Gad added: “Praying for Jeremy Renner and his family.”
“My sweet Jer,” fellow Marvel star Tara Strong (Loki) wrote. “Loved you for decades. From a Senior Trip to the #MCU. Sending you & your closest healing love, light & strength for a full recovery.”
The actor’s family confirmed on Monday (2 January) that he was in a “critical but stable condition”.
“We can confirm that Jeremy has suffered blunt chest trauma and orthopaedic injuries and has undergone surgery today (2 January),” Renner’s family said in a statement. “He has returned from surgery and remains in the intensive care unit in critical but stable condition.”
Renner’s loved ones have also said they have been “tremendously overwhelmed and appreciative of the outpouring of love and support”.