Within three minutes Carroll fired home from the edge of the area to secure a point which edged the Hammers closer to safety and left Stoke still in serious trouble, four points from safety.
Carroll's late strike spares the blushes of teammate Joe Hart, whose mistake allows Peter Crouch - another second-half substitute - to put Stoke ahead in the 79th.
Fit-again striker Carroll climbed off the bench to volley a last-minute equaliser on his first appearance since the turn of the year.
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David Moyes' men came into the clash looking to build on their 1-1 draw with Chelsea last time out, while the Potters were hoping to bounce back from a loss to Tottenham Hotspur. "It's been tough, but I'm back on the pitch now, so it's all good", he said. "If they had played like that since August I wouldn't be here and we wouldn't be in this position".
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West Ham ace Carroll reflected on the last-gasp handball that put paid to a potential victor from Javier Hernandez. The Mexican global has scored eight goals this season, including four in his last eight games.
Michael Oliver was refereeing a game for the first time since his controversial penalty award at the end of the Champions League quarter-final between Real Madrid and Juventus, a decision which led to abuse being directed towards his family on social media.
Southgate was at the London Stadium on Monday night to run the rule over Hart, who was named in West Ham's starting line-up against Stoke, and Butland.
He'll be eager to score against his former employers that's for sure, just like he did in the reverse fixture in December, and I can see the highly talented Austrian getting on the scoresheet at some point during the game if the Hammers click into top gear. "He got unfairly criticised from a lot of quarters".
"He had two very similar shots in the first half and he took them comfortably".
"We've been playing well".
Lambert had to be fearless and he was when he brought on 37-year-old Crouch for Bauer, who was playing in midfield but is usually a defender.