LONDON -- There is something particularly brutal about a heavy defeat in the Champions League. Nothing exposes a team's weaknesses quite like a dismantling by a side from another league, and Chelsea know precisely how that feels after being given a lesson by Bayern Munich at Stamford Bridge on Wednesday night.

This was the moment when the full scale of the rebuilding job still to be done at Chelsea became apparent. Home defeats against the likes of Bournemouth and West Ham in the Premier League are one thing, but a 3-0 defeat against Bayern -- and it could have been much worse -- served only to reveal the huge gulf between the 2012 Champions League winners and Europe's elite.

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"It was a harsh lesson in the reality of Champions League football," Chelsea manager Frank Lampard said. "We have to improve in the summer, and today was a clear show that there is a lot of work to be done.

"I felt that when I came in the summer, and I still feel that today."

In some ways, this defeat could actually help Lampard get the players he wants and needs to take Chelsea to the higher level they used to take for granted. But the truth is that Hansi Flick's Bayern coasted to their Round of 16, first-leg victory following two goals from Serge Gnabry and the other from Robert Lewandowski, as the German champions made next month's second-leg at the Allianz Arena a formality.

Bayern will sail on into the quarterfinals, having injected youth and pace into the team since last season's last-16 elimination against Liverpool, but where Chelsea end up is anyone's guess. Lampard has arguably over-performed with the squad he inherited from Maurizio Sarri last summer -- a squad that lost its best player, Eden Hazard, to Real Madrid last summer and one that couldn't be strengthened due to a two-window worldwide transfer ban, which was subsequently reduced to one window on appeal.

That Chelsea are still in the Premier League top four, having won just five of their last 15 league games, highlights how well they started the season under Lampard, but reality has been biting hard for a while domestically. Bayern's performance was the equivalent of throwing a bucket of ice-cold water everyone at Stamford Bridge, just to make sure they all realise the state Chelsea are in.

This is a club that will always measure itself against the best in Europe. Since Roman Abramovich transformed Chelsea from also-rans into one of the continent's most powerful clubs following his arrival as owner in 2003, they have won three European trophies (one Champions League and two Europa Leagues) and lost a Champions League final on penalties. By and large, Chelsea have been a Champions League regular since 2003, but they looked like novices against Bayern, who were clinical in the second half after letting the home side off the hook during the opening 45 minutes.

"That's football at this level," Lampard said. "The levels of Bayern Munich were fantastic. They are a really strong team. Unless we had a 'bang on' night, it was going to be tough and that's what happened.

"When you have an eye-opener like tonight, no matter how young or old you are, you have to look against your direct opponent and ask what lessons you learned. But in the bigger picture, we saw the quality in their team. Lewandowski has been there a long time, and [Thomas] Muller, [Manuel] Neuer, [Jerome] Boateng: I played against all them in 2012 in the final. They have been together for a long time."

Longevity and stability are not something that this Chelsea squad has been blessed with. The young players who have been given a chance by Lampard this season -- Mason Mount, Tammy Abraham, Reece James -- will be fine servants for the club for years to come, but there are still plenty of big gaps to be filled. Defense remains an issue, as does the heart of midfield, but the biggest problem seems to be in goal, where the steady (but hardly spectacular) Willy Caballero continues to be preferred ahead of the out-of-form (and club-record signing) Kepa Arrizabalaga.

The inability to spend last summer and failure to take advantage of the lifting of the transfer ban ahead of the January window has left Chelsea painfully short of the quality required to compete at this level. Lampard was without the injured N'Golo Kante, Christian Pulisic and Callum Hudson-Odoi for this game and it showed. All three are doubtful to be fit for the second leg in Munich and Lampard will also be without Marcos Alonso, sent off in this game, and Jorginho due to suspension.

That said, Chelsea's challenge is not about achieving a Champions League miracle by overturning their first-leg deficit in Munich. It's about the long term and being able to build a squad capable of once again making Chelsea a heavyweight contender in the Champions League. They have some foundations in place under Lampard, but time will tell whether they are strong enough to keep their legendary former player in a job.

On this evidence, though, it will take at least two years to get close to Bayern's level. Lampard's problem is Chelsea have rarely shown such patience since Abramovich took over.