Martinez capped a big night at Old Trafford by bundling in United's fourth goal in front of the Stretford End as Ruben Amorim's side thrashed Azerbaijani outfit Sabah 4-0 in the Champions League on Thursday. Yet with Manchester City visiting for the derby on Sunday afternoon, the World Cup winner was quick to temper any growing confidence.
"When you win, your confidence is going up, you know, but now we have to be calm, we have to be humble," Martinez said. "Then tomorrow we have to think about the derby that is really important for us."
Despite Manchester United's momentum in Europe, Martinez played down suggestions that the club is now ready to challenge for major honours this season.
"It's too early to say that," he said. "We just have to be ready every game, we have to be humble, have to enjoy, have to fight every game, and we know what we want, but I can't tell you if we will challenge at the top this season."
The win over Sabah was notable not just for the goals but for United's first clean sheet of the campaign, following games against Hull City, Ipswich Town and Everton in which they had conceded twice apiece. Martinez admitted the defensive lapses, particularly at Hull and late on against Everton, had frustrated the squad.
"It will always be a responsibility for us to keep clean sheets, but I think against Everton, I think we played to take the clean sheet and then we conceded the goals, that's what annoys us," he said. "It's really bad, for sure, because we want to be there, and if we want to compete, we have to keep the clean sheet because it's very important. Today we did it and we have to build on that."
Looking ahead to the visit of Pep Guardiola's City, Martinez insisted United could not afford to dwell on their midweek form.
"That is the past. It's gone and now I have to be ready for this game because it's going to be so different than the last one," he said.