Chelsea ended pre-season unbeaten for the first time since 2011 as young Mason Burstow headed a late equaliser to secure a 1-1 draw with Borussia Dortmund.

Playing on an absolute disaster of a pitch, both teams found it incredibly difficult to string passes together but Chelsea were still by far the better side and could easily have scored four or five on another day.

In the end, it was Dortmund who nearly emerged victorious when Marius Wolf tapped home with ten minutes to go, but Burstow leapt highest in the 89th minute to nod in and close out pre-season on a positive note.

Here's a look back at all the key points of the action.

Pitch ruined by Ed Sheeran concert

Soldier Field hosted an Ed Sheeran concert earlier this week and the fans in attendance were allowed on the pitch to get up close and personal with the star. Unsurprisingly, the turf was left in tatters, and Chelsea had to pay the price.

Passes were bobbling everywhere and it made for uncomfortable viewing at times, with both sets of players visibly frustrated.

There were obvious concerns about potential injuries, and those fears came to life for Chelsea.

Christopher Nkunku limps off injured

Christopher Nkunku lined up on the left side of Chelsea's attack but managed just 22 minutes before limping off with a knee injury.

The Frenchman's pre-season was brought to an abrupt end when he went down in the box, and after he limped off, he was seen sitting on the bench with a knee brace.

Manager Mauricio Pochettino made a point of stressing the pitch was not responsible for his injury, but many fans weren't so sure.

Reece James wears the captain's armband

Both Reece James and Thiago Silva started for Chelsea, with the former wearing the captain's armband.

With Chelsea yet to announce a new permanent captain, James and Silva have shared the responsibilities this summer as they took turns on the pitch, but with both starting together, Pochettino opted to put his faith in the homegrown right-back.

It doesn't necessarily mean anything, but it's hard not to think this could be a glimpse into Pochettino's upcoming decision.

Wolf taps home to punish profligacy

Chelsea have scored plenty of goals this summer but flashed signs of their form over the past few seasons against Dortmund as they missed chance after chance after chance.

It looked like Chelsea were going to be punished for their wastefulness in front of goal when, ten minutes from time, Marius Wolf popped up in the box to tap beyond Kepa Arrizabalaga after beating the offside trap.

Chelsea fans are no strangers to watching their team lose these kinds of games, but thankfully, there was a different story this time around.

Burstow saves the day

19-year-old striker Mason Burstow is expected to leave Chelsea on loan when he lands back from the United States, and if he does leave, he will depart knowing he was responsible for saving the Blues' unbeaten pre-season.

With 89 minutes on the clock, Burstow rose highest in the box to steer a looping header away from the goalkeeper and into the back of the net, capping off a solid summer from the academy star.

Burstow, who has League One experience with Charlton, will now hope to keep that momentum going as he embarks on the next chapter of his Chelsea career.

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This article was originally published on 90min as Chelsea 1-1 Borussia Dortmund: Pictures & talking points from pre-season friendly in Chicago.