The Serie A champions have remained true to Italian form by limping through the group stages, losing twice, drawing twice and winning convincingly only once.
They had already qualified for the knockout stages ahead of Tuesday's game at Werder Bremen but Mourinho still wanted a win even if he queried the value of finishing top of Group B.
As it was his side put in another lacklustre display to lose 2-1 with wingers Mancini and Ricardo Quaresma, big money arrivals from AS Roma and Porto in the transfer window, beginning to look major flops.
Inter striker Zlatan Ibrahimovic, easily their best player this season thanks to his goals and creative spark, was meant to be rested for the Werder game but Inter were so poor that the Swede was thrown on at halftime and scored a superb consolation.
Former Chelsea coach Mourinho, picked to replace Roberto Mancini in June mainly because of his Champions League pedigree, did not mince his words when laying into his players after last month's lifeless 1-0 home defeat to Panathinaikos.
He has tried a different tactic following the Werder defeat, hinting that the group had looked too easy on paper and that his side will only rise to the occasion against big teams.
"The real bad luck will be for the top side in another group who will draw a tough team like Inter," Mourinho told reporters.
"I am sure that we will see the true Inter at the end of February."
BEST PERFORMANCES
The Portuguese's habitual confidence is based on Inter's displays against big sides in Serie A this term.
They are six points clear at the top thanks to their best performances of the season in a 4-0 victory at Roma, a 1-0 win over Juventus and last weekend's 3-0 triumph at Lazio.
Inter in contrast have struggled against the smaller sides, who have defended in numbers and exposed a lack of creativity in Mourinho's midfield.
The coach, who won the Champions League with Porto in 2004 and took Chelsea to two semi-finals, believes drawing Manchester United or Barcelona will also bring the best out of his side.
But Inter's European form over decades tells another story.
Winners in 1964 and 1965, Inter have flattered to deceive in the European Cup ever since and never come close to challenging.
It will take a lot more than some one-off good performances and a sprinkle of Ibrahimovic magic for them to become a real threat.
Mancini won three Italian titles in a row but his failure in Europe ultimately cost him. Mourinho knows the score.
Fast improving AS Roma, who beat Bordeaux 2-0 on Tuesday to progress to the knockout stages, and already-qualified Juventus have played substantially better than Italian rivals Inter in the group stages.
Mourinho may think the pair have peaked too soon but confidence is also a wonderful asset.
