Robert Lewandowski didn't expect to meet his former club so soon. Neither did Erling Haaland.

After switching sides this summer, Lewandowski returns to Bayern Munich with Barcelona in the Champions League group stage on Tuesday, while Manchester City striker Haaland is set for a quick reunion with his former Borussia Dortmund teammates on Wednesday.

Haaland scored twice in City’s opening 4-0 win at Sevilla last week and has 25 goals in 20 Champions League appearances overall. He has 10 goals in six Premier League appearances already this season for City.

"The #UCL is back and I love it!" the 22-year-old Norway star wrote on Twitter.

Lewandowski is also in top form, coming off the bench to score his sixth goal in five Spanish league games to help Barcelona win 4-0 at Cadiz on Saturday.

The Poland striker has only failed to score on his debut – against Rayo Vallecano – since he forced his move to Barcelona from Bayern in the offseason.

Lewandowski also got a hat trick in Barca’s opening 5-1 rout of Viktoria Plzen in the Champions League last week, taking his tally to 89 goals in that competition. He became the first player to score a hat trick for three different clubs in the Champions League.

Barca fans – who also fondly remember Lewandowski's four goals for Dortmund against Real Madrid in 2013 – are hoping he proves the difference against a team that has swept it aside in recent seasons.

Bayern humiliated Barcelona 8-2 in 2020 and beat the Spanish club twice by the score of 3-0 last year.

Bayern and Dortmund go into their matches after disappointing performances in the Bundesliga on Saturday.

Dortmund slumped to a 3-0 loss at Leipzig and Bayern was held to its third consecutive league draw by Stuttgart.

"We have to up it by two gears, against Barcelona by three," Bayern sporting director, Hasan Salihamidzic, said.

Dortmund won its opening Champions League game 3-0 at home against Copenhagen but feels it needs to make amends in Manchester for the Leipzig defeat.

"We were already in Manchester not so long ago and we showed we can be a surprise," Dortmund sporting director Sebastian Kehl said about his side’s 2-1 loss to City in the first leg of the quarterfinals in 2021.

Haaland was playing for the German team at the time, however.

Also, this week, defending champion Real Madrid welcomes Leipzig on Wednesday, when Juventus hosts Benfica and Paris Saint-Germain visits Maccabi Haifa.

On Tuesday, Liverpool will hope to answer its crushing 4-1 opening loss at Napoli with a good result against Ajax.

Bundesliga giant Bayer Leverkusen will host Atletico Madrid while Tottenham visits Sporting Lisbon.

Europa League winner Eintracht Frankfurt, in the meantime, will travels to Marseille for what’s considered a high-risk game between rival fans.