CHELSEA’S second string maintained their 100 per cent record in the third tier of European competition - but not without a number of scares.
Top scorer Christopher Nkunku claimed his seventh goal in the Europa Conference League and on another night might have had a hat-trick.
But Heidenheim, who also went into the game with three wins from three, caused plenty of problems for the Blues.
Blues goalkeeper Filip Jorgensen made a string of saves, the best of them after Nkunku’s goal and before Mykhailo Mudryk sealed victory with less than five minutes to go.
And apart from Jadon Sancho, none of the other outfield players in the cream-coloured kit made much of a case to rise into the first 11 for Sunday’s clash with Aston Villa.
As usual Enzo Maresca made wholesale changes from his first 11, with only Benoit Badiashile keeping his place from the win at Leicester.
READ MORE ON CHELSEA
But Chelsea learned within a minute that it would not be another Thursday night stroll.
Badiashile was booked for fouling Heidenheim winger Leonardo Scienza and Mikkel Kaufmann almost touched in the resulting free kick.
It was an entertaining, end-to-end game in a festive atmosphere.
Marc Guiu, twice, and Kiernan Dewsbury-Hall had shots saved, while Jorgensen denied Kaufmann, Scienza and Mathias Honsak.
Most read in Football
CASINO SPECIAL - BEST CASINO WELCOME OFFERS
After Nkunku spooned a finish over the bar, Chelsea were awarded a penalty when Mykhailo Mudryk went flying over a challenge by home captain Patrick Mainka.
But Dutch referee Serdar Gozubuyuk went back on his decision after being summoned to the VAR monitor.
Nkunku drew another save from home ‘keeper Kevin Muller, Tosin Adarabioyo shot just wide and the half somehow ended 0-0.
Heidenheim had another chance before Nkunku broke the deadlock.
Sancho’s cross sat up nicely and the France international found a fine finish.
The home side, with their supporters keeping up constant noise behind the goal they were attacking, kept going and Scienza curled a shot just wide.
Chelsea ratings vs Heidenheim
Chelsea remained at the top of the table with a hard-fought 2-0 win over Heidenheim.
Christopher Nkunku and Mykhailo Mudryk got on the scoresheet as the Bundesliga side gave them their toughest test so far in the Conference League.
The Blues were not at their best in the opening 45 minutes but were far better after a half-time team talk from Enzo Maresca.
Click here to see how SunSport's Alex Smith rated the Chelsea performances.
Wanner should have equalised, but Jorgensen made a fine save and then another from Scienza’s follow-up.
Substitute Joao Felix sent Nkunku through on the break but Muller kept his team in it with another save.
Home sub Maximilian Breunig had the ball in the net but it was ruled out for offside and Muller denied Dewsbury-Hall at the other end.
READ MORE SUN STORIES
Mudryk finally killed the game with an emphatic shot into the top corner after more good work by Sancho.
Cesare Casadei was sent off for a second yellow card deep into stoppage time, which reflected a tough but ultimately successful evening for the Blues.