Spurs found themselves trailing by two goals after early defensive errors allowed Jay Rodriguez and Adam Lallana to give the visitors a clear advantage within half an hour.
But a double from Christian Eriksen and a late winner from Gylfi Sigurdsson - a half-time substitute for Mousa Dembele - sealed a dramatic victory for the hosts, leaving Sherwood delighted with his side's character and work-rate.
"A lot of people write what they want about the players turning it in," the 45-year-old told reporters. "They haven't turned it in, have they?
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"I have to be honest, I just think we needed to tweak it. We needed a bit of energy in the midfield. Mousa [Dembele] lacked energy in there, he hadn't trained all week. Gylfi gave us energy."
Sherwood also feels that Tottenham's Europa League exploits in Lisbon played their part in a lethargic start, admitting that his half-time team talk was "not pretty" as a result.
Asked what he said to the players during the break, the Spurs boss replied: "I can't tell you everything! It wasn't pretty.
"I wanted to play a high-tempo game and try and press them high up the field and I didn't think we had the energy to do it. I have to make an excuse for them and say their European games took their toll. We didn't start well and, against a good team like Southampton, you'll get punished."
Meanwhile, Saints boss Mauricio Pochettino was left unimpressed with a number of refereeing decisions that went against his side at White Hart Lane - notably in the build-up to Tottenham's first goal.
"We were 2-0 up and controlling the game. Their first goal came from a clear foul on Dejan Lovren [by Roberto Soldado] so it should never have stood," the Argentine complained.
"It was a heavy punishment for us. I thought we did really well against a good Tottenham side but some refereeing decisions did not go for us.
"Mathematically, it's still possible to get into Europe but we have to see if the reality of the team is that we can play in Europe."