Despite breaking the deadlock through yet another Luis Suarez goal at Anfield, a brace from Jan Vertonghen had afforded the visitors a commanding position as the match entered its final quarter.
But a defensive mix-up by Spurs handed Downing the chance to claim his fifth strike of the season - levelling the score in the process - before Steven Gerrard converted a spot-kick to secure three points.
The triumph was the fourth on the run in all competitions for Brendan Rodgers' team and the 28-year-old Downing reflected post-match that it may have been their most impressive so far.
"Earlier in the season we would probably have lost the game," he told Liverpoolfc.com.
"But great credit to the lads, we kept going and the fans were right behind us. I'd say it was probably one of the best wins of the season."
Downing's awareness allowed the wide-man to take full advantage of a misplaced Kyle Walker back pass and poor goalkeeping on the part of Hugo Lloris to equalise on 66 minutes.
The England international also showed great composure when his opportunity arrived, passing up the option of teeing up Daniel Sturridge and instead drilling his finish into the Kop End net.
He added: "I did think of chipping at first but if you put your foot through it, the worst that can come is they clear it.
"I'm sure Daniel wouldn't have been happy if I didn't score. But I was in the position and lucky for me, it went in.
"I'm full of confidence, even without the goals. Playing in a good team and playing well gives confidence.
"There's no hiding from the fact that I struggled for goals last season, but this season I'm in among them and hopefully I can get plenty more - there's plenty of games to go to get the tally up.
"The manager has got options now - if people are having an off day, they can always put someone on and they're liable to get a goal.
"It was nice for me to get a goal, Luis got another one and Stevie scored a good penalty."
Sunday's result was the first time the Reds have beaten a side in the top five of the Barclays Premier League this season and saw Liverpool rise to sixth in the standings with nine games remaining.
Downing warned that confidence is soaring around the Anfield dressing room and feels that Champions League qualification could still be within reach.
"It shows in the results - the 5-0s, 4-0s and 3-0s. After going behind today, we proved that we can match the big teams," the former Middlesbrough and Aston Villa man said.
"A lot of people have been saying we can't beat teams in the top five or six - that's out of the way now. Hopefully that will kick us on.
"We want to go into the last 10 games and win as many as possible. That's the target we set. It was a great win for us and will give us a lot of confidence going into the next games.
"We're certainly good enough as a team, we've proved that and that is a big victory - beating one of our rivals, who are third in the league.
"We've got a hell of a chance. We'll just finish the season well and then next season, with a few additions, we can kick on."