Inter grabbed two early goals through Edin Dzeko (37) and Henrikh Mkhitaryan (34) to secure an impressive 2-0 win over Milan in the first leg of their Champions League last-four tie on Wednesday, taking a significant advantage into next week's return encounter.
One of the two sides will become the first Italian finalist since Juventus faced Real Madrid six years ago, but a potential showdown against powerhouses Real or Manchester City leaves them no room to relax on the domestic front.
Neither of the Milan-based clubs can be assured of a top-four spot just yet, with Inter fourth in the standings on 63 points and Milan right behind, on 61.
Inter could not have timed their return to form any better as Simone Inzaghi's men are on a six-game winning streak in all competitions, four of them in Serie A.
A home win against mid-table Sassuolo on Saturday could bring some breathing space ahead of their return leg with their rivals on Tuesday.
For Milan, who face Spezia on Saturday, things are different and last year's Serie A champions have little room for error left.
Milan have won only two of their last six games on the domestic front, with four draws, and they need to quickly rebound from their Champions League disappointment if they want to return to the competition next season.
"I will try to make the best choices to try to win against Spezia and then overturn this (semi-final) result," Milan coach Stefano Pioli said following their defeat to Inter.
"Playing as Milan, playing better, with quality and intensity" is the way forward, according to the coach.
As well as lowly Spezia, Milan face already-relegated Sampdoria and struggling Hellas Verona in three of their remaining four league outings but all are must-win matches given Pioli's side also have to visit second-placed Juventus.
Spezia, who are 18th, have not won any of their last eight games and on Saturday could register their longest ever streak without a Serie A victory.
For third-placed Lazio, three losses in their last four games have shaken things up at the capital club, and a home game against 16th-placed Lecce may help them regain some much needed balance.
"At half-time I saw a disheartened team and this is the aspect that worried me the most," coach Maurizio Sarri said after their 2-0 loss at Milan last weekend.
Lazio had recorded seven wins and one draw in eight Serie A matches before their form nosedived, which saw them drop from second to third in the table, one point ahead of Inter.
Champions Napoli will travel to Monza on Sunday after their fans got to celebrate the title with a home win over Fiorentina last week.
Juventus will host second-bottom Cremonese on Sunday in between their two Europa League semi-final matches against Sevilla.
