United were two goals down at half-time after careless errors by Patrice Evra and Nemanja Vidic gave away two penalties but a Wayne Rooney hat-trick and a goal from Javier Hernandez gave the visitors a 4-2 win that edged them closer to a record 19th title.
"I think we played like champions today," Ferguson told Sky Sports. "We kept our heads up and didn't lose faith in our ability and that was a great, great boost.
"We dominated that second half and it was a real championship performance as far as I'm concerned."
Ferguson, watching from the stands while serving the second game of a five-match touchline ban, spent much of the first half chomping furiously on his chewing gum as his side went 2-0 down after 25 minutes.
An Evra handball and a trip by Vidic on the edge of the area handed West Ham two spot-kicks which Mark Noble converted.
It could have got even worse for the leaders as Vidic escaped with only a yellow card after hauling down Demba Ba when the West Ham striker looked poised to go clear on goal.
"He could have been sent off," said Ferguson. "I thought he got maybe a lucky break. It would have been harsh but he could have been sent off for it."
Just as they did against Blackpool in January, United found themselves trailing by two goals at the break and just as they did on that occasion they transformed their fortunes after some clever substitutions.
Ferguson brought on livewire Hernandez at the start of the second half, moved winger Ryan Giggs to an unfamiliar left-back position and later sent on top scorer Dimitar Berbatov as the earlier defensive shakiness faded into insignificance.
"We had a strong bench today," said Ferguson who had goal poacher Michael Owen and Brazilian midfielder Anderson among his unused substitutes and only used winger Nani late on with next week's Champions League quarter-final first leg at Chelsea looming.
"I just felt we had to go for it. I brought on Chicharito (Hernandez), put Ryan to left-back, at that point I said to myself goal difference doesn't matter here. Let's get something out of it and we managed to change the game round."
Rooney, who scored an excellent curling free-kick, low drive and spot kick to notch a hat-trick in the space of 14 minutes, agreed the changes made the difference. "I think the substitutions were good substitutions and that's what won us the game," he told Sky Sports.
United have won only five of their 16 away league games this season but have continued to salvage important points as they seek to repeat their 1999 treble in the league, FA Cup and Champions League. They are eight points clear of second-placed Arsenal who have played two games fewer.
"Even when we've not been playing well we've been grinding out results so hopefully now with seven games to go we can keep doing that," said Giggs.
Thank you for reading 5 articles this month* Join now for unlimited access
Enjoy your first month for just £1 / $1 / €1
*Read 5 free articles per month without a subscription
Join now for unlimited access
Try first month for just £1 / $1 / €1