Daryl Murphy's last-gasp header pinched the points for Ipswich over Blackpool, who thought they had rescued a point with an injury-time leveller from Steve Davies at Bloomfield Road.
Stephen Dobbie had put Blackpool ahead with a first-half header, but the visitors took the lead thanks to goals in the second half from Nouble and Paul Taylor.
The Ipswich boss revealed he had had a strong word with Nouble in the week.
"I had a snarl at Frank (Nouble) in training - I wasn't happy with him and he's shown me what he can do," said McCarthy.
"I told him that's the way to show me. I don't take poor performances. You can play badly but put everything in.
"We had a pretty awful first half. I worked in training on what ifs," he added.
"We had three up front and one behind and three or four different shapes.
"I did it for that reason. Very often we played 4-4-2 and you have to change the shape. It's paid dividends thankfully.
"Dobbie was causing us problems in behind and we were too focused on him rather than our own things. I thought Frank and Murphy had good chances."
Blackpool assistant boss Alex Rae struggled to hide his disappointment after the defeat to Ipswich.
"It's very disappointing. We pride ourselves on our defence and to lose the game from bad defending is disappointing," Rae said.
"We've scored a lot of goals in the last 10 minutes of games and I thought we'd snatched a point.
"We told them Murphy was a threat from set-pieces - he scored from one against Barnsley last week - but we didn't deal with him at all.
"But when all is said and done, we've only lost twice in the first three months of the season and we've made a good start."