The 36-year-old actor said he could not help but also worry about his own future when his veteran co-star caught her shoe on her dress as she jumped on a table during a rehearsal, reported Contactmusic.
"(She) starts to fall back, head first. Time slowed down and I thought, 'I'm about to watch Meryl Streep die. It's happening.' I wish I could say I didn't consider my own career in this," he recalled.
While Corden and director Rob Marshall 'froze', Emily Blunt, who was pregnant with her daughter Hazel, now 10 months, leapt in to save her co-star.
The British star also admitted he was initially in awe of being around the 65-year-old acting legend.