Ole Gunnar Solskjaer said it was a "good job done" rather than job done after Manchester United thrashed Roma 6-2 in the UEFA Europa League semi-finals.
Bruno Fernandes gave the Red Devils an early lead in a dramatic first leg at Old Trafford on Friday (AEST), but Lorenzo Pellegrini's penalty and a goal from Edin Dzeko put Roma 2-1 up at half-time.
The luckless Giallorossi lost three players to injury in the first half - including goalkeeper Pau Lopez - and they were torn apart by a rampant United after the break.
A brace from the magnificent Edinson Cavani put the Premier League side back in front and Fernandes had a double of his own when he made no mistake from the penalty spot.
Paul Pogba and Mason Greenwood added further goals to put United on the brink of a final against either Villarreal or Arsenal in Gdansk on May 26.
Ruthless United scored six or more goals in a single match in European competition for the first time since netting seven against Roma in April 2007; they are also the first side to net as many in a major European semi-final since Real Madrid in the European Cup in May 1964.
Still, Solskjaer says there is no chance they will be complacent heading into the second leg at the Stadio Olimpico next Friday.
The Red Devils boss told BT Sport: "No I don't feel the job is done but it was a good job done. We did well but we know they have quality.
"They scored two goals from the two chances we gave them. They didn't have loads of chances against Ajax. The second half was very good."
Solskjaer was impressed with the way his side stormed back after surrendering a first-half advantage.
"We took most of our chances today, so we're very pleased. The character showed – we came back, we didn't lose our heads," he added.
"For five, 10 minutes at the end of the first half we didn't look great, but we got it together."
Roma were unable to make any further changes in the second half after losing Jordan Veretout, Lopez and Leonardo Spinazzola in the opening 45 minutes.
Under-pressure coach Paulo Fonseca rued their misfortune but was at a loss to explain such an astonishing second-half capitulation.
He told Sky Sport: "It's difficult to explain how the same team that did so well in the first half had that kind of second half. It's hard to play against a side like United without having the substitutions.
"It's positive to reach this stage of the competition anyway, and also to play like we did in the first half. But in the second half we got everything wrong."