Last season’s beaten finalists triumphed 1-0 at St James’ Park, and then saw themselves drawn against City’s derby rivals Manchester United – their conquerors at Wembley in February – at Old Trafford.
For Magpies head coach Howe, it was a first win in 14 attempts against Guardiola as a manager, but that was not his main cause for celebration.
Howe said: “Yes, my record against him isn’t good, so it’s nice to win, but most importantly it’s not about that it’s about trying to progress in the competition and I’m delighted with the players, delighted with the efforts that they gave.
“It was a very difficult game for us in that first half, I thought they played very well. I thought we defended very well – we had to because we struggled, didn’t have much rhythm.
“But then the second half was a totally different performance. The balance of of the team was much better and I’m delighted with everyone’s commitment to the game.”
While Howe chose to rest 10 of the men who started Sunday’s 8-0 Premier League demolition of Sheffield United, opposite number Pep Guardiola made eight changes, although it was the way in which they used their respective benches which ultimately proved decisive.
The Spaniard kept star striker Erling Haaland in reserve and asked substitute Phil Foden to try to rescue the tie for him, while his opposite number changed the pattern of the game by sending on Bruno Guimaraes and Anthony Gordon at the break and reaped the rewards.
Newcastle have already lost to City and Liverpool in the league this season, so victory over one of the big boys was all the more welcome.
Howe said: “The only way you go into these games with more belief is by winning, so hopefully that will serve us well for the future. It shows that we are capable.
“Yes, both teams made changes, but all you can do is try to win the game and we did, and I’m delighted with the players.”
The game was settled by Alexander Isak’s 53rd-minute finish at the end of a powerful run by Joelinton, although City were left kicking themselves for not capitalising on their domination before the break and their failure to mount a fresh charge after it.
Asked if he was disappointed that his side could no longer win a quadruple to go with the treble they landed last season, a bemused Guardiola said: “You think the target was to win the quadruple? Honestly, it’s not.
“We competed really well and we are more than satisfied to win the treble. Our expectations are high, but not high enough to not be satisfied with that.”
Guardiola opted not to throw Haaland into the mix as time ran down, and was happy to defend that decision.
Asked if he considered sending the frontman on, he said: “No. I thought Kyle (Walker had played) a lot of minutes, Erling a lot of minutes. We have a lot of games ahead of us.
“Maybe the last 10-15 minutes, but I decided not to do it.”