Porto suffered the agony of being by outwitted by their former coach on Wednesday as the Champions League holders slumped to a 3-1 defeat at Jose Mourinho's Chelsea.
AC Milan snatched a late 3-1 win over Celtic at the San Siro, Inter Milan beat Anderlecht by the same score in Belgium and Barcelona trounced Shakhtar Donetsk 3-0 as the night's action went largely according to form.
Late goals steered Werder Bremen to a 2-1 home victory over 10-man Valencia and PSV Eindhoven to a 1-0 win over Panathinaikos, but there was only frustration for England's champions as Arsenal were held 1-1 at Rosenborg Trondheim.
CSKA Moscow recorded their first ever Champions League win by beating ailing Paris St Germain 2-0 on another entertaining night that added 23 goals to Tuesday's 31-goal bonanza.
Several teams will be returning home believing they have one foot in the knockout phase while others, such as Porto, will know they are already in deep trouble.
Chelsea fit comfortably into the former category after following up their 3-0 win over PSG a fortnight ago with a convincing victory at Stamford Bridge to lead Group H on six points.
The meeting between Mourinho and the club he guided to consecutive UEFA Cup and Champions League trophies, along with two Portuguese league titles, had been one of the competition's showcases since the draw was held last month.
MOURINHO'S MEN
Alexei Smertin gave Chelsea an early lead, Didier Drogba added a second after the break and John Terry put the game out of reach after Benni McCarthy had pulled one back for Porto, much-changed since Mourinho's close-season departure.
The Portuguese champions, held to a goalless draw by CSKA a fortnight ago, have garnered only point in the defence of their title and trail the Russians by three.
Group F is also taking shape with Barcelona and Milan both racking up six points while Shakhtar and Celtic have yet to get a point on the board.
Though Shakhtar were never in with a chance against Barca, who scored through Deco, Ronaldinho and Samuel Eto'o, Celtic suffered a second European heartbreak in as many weeks.
On the verge of registering their first away point in the Champions League at 1-1, Celtic were floored by an 89th minute strike by Filippo Inzaghi and a stoppage-time goal by Andrea Pirlo.
It was all too familiar for Celtic fans, whose team was drawing 1-1 with Barcelona a fortnight ago with 12 minutes left only to lose 3-1.
KEY DISMISSAL
Inter's second consecutive win, courtesy of goals from Obafemi Martins, Adriano and Dejan Stankovic, secured them a three-point lead over both Werder Bremen and Valencia in a wide-open Group G.
Though it was not his most important goal this year, substitute Angelos Haristeas grabbed Bremen's winner with six minutes to go as Valencia paid a high price for defender Carlos Marchena's 55th minute red card.
Leading 1-0 at the time, their early lead lasted only another five minutes as Miroslav Klose equalised before Haristeas, whose goal won the Euro 2004 final for Greece against Portugal, added the killer blow.
Arsenal's draw, disappointing for a free-scoring team who are unbeaten in a record 47 Premier League games, kept them top of Group E on four points, one ahead of PSV and Panathinaikos.
Arsenal have consistently under performed in the Champions League, failing to ever reach the semi-finals, and were given a timely reminder of their fragility in Norway.
Swede Fredrik Ljungberg gave them a sixth-minute lead but the failure of Arsene Wenger's much-vaunted side to take their chances was eventually punished by Roar Strand's equaliser in the 52nd minute.
Jan Vennegoor of Hesselink, who missed a late sitter in PSV's 1-0 defeat by Arsenal two weeks ago, made amends with a match winning header in the 80th minute against Panathinaikos.
