5 things we learned from Matchday 5: Cavani frustrates, Bayern falters

The Champions League group stage is entering its final round of action, yet there are still plenty of questions left to be answered.

Here are five things we learned from this week's slate:

Cavani both a big scorer and bottler

There's no denying Edinson Cavani has done his best to replace Zlatan Ibrahimovic. He's leading Ligue 1 with 11 goals, and his 16 tallies across all competitions are bettered by no other player in the big five European leagues.

He got a foot on the end of an inviting Blaise Matuidi pass to give Paris Saint-Germain an early lead in Tuesday's 2-2 draw with Arsenal, but this outing was again filled with missed opportunities. The 29-year-old Uruguayan seemingly could've bagged a hat trick, had he directed more of his efforts on goal.

In one mad flurry toward the end of the second half, Cavani nodded two prime headers wide of David Ospina's net. On another occasion, the former Napoli poacher sprinted free of every Arsenal player, yet could only muster a feeble lob that Ospina collected with ease.

(Courtesy: FourFourTwo)

In other words, Cavani is a paradox. Despite his talent, he's a serial bottler from high-percentage situations. His conversion rate hovers around 25 percent, which is actually quite good, but it could - and probably should - be much better. He makes the difficult look easy, and the easy look difficult - and that's why he's not considered the best No. 9 around.

Cavani's overall game is fantastic. His movement is fleet, and his awareness is honed. That he often finds himself in position to score is a testament to his predatory instinct.

But Cavani's reputation takes a hit because he cannot execute when the moment calls for a simple finish.

Tottenham unprepared for the big time

Tottenham's temporary move to Wembley was supposed to herald a new era. Instead, it became the burial ground for its Champions League hopes.

Consecutive home defeats to Monaco and Bayer Leverkusen ultimately dealt Mauricio Pochettino's side the fatal blow, even if Tuesday's 2-1 loss to the principality club sealed elimination.

The Argentine manager admitted afterward his team must learn to manage the rigours of playing in multiple competitions. Until then, Spurs cannot expect to challenge the game's elite.

For his part, goalkeeper Hugo Lloris showed at Stade Louis II that he's the only Tottenham player at the European level. The Frenchman made several saves - including a Fabinho penalty - that gave his teammates a fighting chance.

In the weeks before this limp defeat, Tottenham simply struggled to produce goal-scoring opportunities. With an average of just 2.6 shots on target per match - fifth-worst among Champions League group stage sides - the Premier League outfit showed a severe lack of ruthlessness in front of goal.

Bayern vulnerable to individual mistakes

The easy scapegoat for Bayern Munich's unlikely 3-2 away defeat to Rostov is manager Carlo Ancelotti, who made six changes to the squad that played Borussia Dortmund on the weekend. The defending Bundesliga champion could be accused of underestimating the Champions League debutant.

But the reality is that key protagonists made mistakes.

Jerome Boateng - one of the world's preeminent centre-backs - was culpable on Rostov's first two goals. Forced to fill a vacancy ahead of him in midfield, the Germany international couldn't recover when Sardar Azmoun picked up the ball and drove at goal. Boateng fell over and watched the tally from his backside.

Sticking out a lazy foot on Christian Noboa, the 28-year-old later conceded a penalty that allowed Rostov to tie the game 2-2.

Not to be outdone, Thiago Alcantara then gave away the winning free-kick on the edge of the 18-yard box.

Rather than a defeat of Ancelotti's man-management skills, this upset was decided by simple errors. That is much different than a systematic breakdown, or managerial carelessness.

"We made too many mistakes and took it for granted that the opponents were capable of scoring," said captain Philipp Lahm. "We had enough quality on the pitch, there were enough internationals out there. Rotation is no excuse for the defeat."

City questionable with back 3

Pep Guardiola once again deployed an odd-looking 3-2-4-1 formation at Borussia Monchengladbach - a system the Spaniard first experimented with in the first Premier League game of the season.

But Tuesday's back three wasn't equipped to combat Monchengladbach's pace or provide a sturdy foundation for Guardiola's passing football.

John Stones is developing into a fine player who can play the ball out from the back, but he's still not stable enough to act as a sweeper and add that extra layer of security in front of Claudio Bravo. Beside him was a converted full-back in Aleksandar Kolarov and an overzealous defender in Nicolas Otamendi, who's too quick to go to ground.

Together they're a messy combination of defensive talent.

Despite Guardiola's earlier effusive praise for Kolarov - he apparently put in one of the best performances the manager had ever seen in a 2-1 win over Sunderland - the Serbian is often guilty of gifting possession. His bodged clearance led to Raffael's thunderous opener in Wednesday's 1-1 draw.

There was also yards of space between the midfield and defence, a gap that Monchengladbach exposed time and again in the first half.

Free-scoring Dortmund can't hide back problems

There's no doubting Dortmund's goal-scoring ability. Thomas Tuchel's team has bagged three or more goals on nine different occasions this season.

But its ability to bulge the net is as much of a strength as it is a distraction. There are real questions to be asked of the club's defending, which would've cost BVB more games this season without the likes of Pierre-Emerick Aubameyang bailing out his teammates.

Tuesday's topsy-turvy 8-4 win over Legia Warsaw set a Champions League record for the most combined goals scored in a single match; it also illuminated Dortmund's lack of both concentration and similar intensity at the back.

"We will have to discuss the glaring mistakes we are making," Tuchel told Dortmund's website afterward, "both in one-on-one challenges and in shoring the defence up to deal with counters."