Thomas Tuchel’s side were shocked by their Croatian opponents with Mislav Orsic scoring the only goal of the game after 13 minutes.
It was a breakaway goal from the home side, who defended solidly despite Chelsea dominating possession throughout the 90 minutes.
VIDEO: Chelsea goal disallowed with help of semi-automated offside
Pierre-Emerick Aubameyang, who was wearing a mask after being a victim to a robbery last week, was making his debut for the Blues but suffered a disappointing evening.
However, he thought he had capped his first appearance with a goal at the start of the second half.
Matteo Kovacic played a lovely ball over the top for Ben Chilwell to square for Aubameyang.
However, the striker’s celebrations were cut short after the assistant referee raised his flag.
That decision was confirmed by the new semi-automated offside that is being used in the Champions League this season.
The system is in place during this year’s World Cup.
What is Semi-Automated Offside Technology?
“Semi-Automated Offside Technology has been developed to support the video match officials,” explained Johannes Holzmuller, FIFA’s director of football technology and innovation. “So, during the FIFA World Cup 2022 in Qatar, the video operations room will receive an automated alert in case of an offside situation, as well as automatically selected kick point, and automatically drawn offside line within a few seconds after the incident.
“After that the video match officials have to validate the proposed selected kick point as well as the proposed drawn offside line. The VAR communicates the final decision to the referee on the pitch.”
“In terms of accuracy, it is important because when you are more accurate it’s good,” added Pierluigi Collina, the chairman of the FIFA referees’ committee. “In terms of time, I think it’s more psychological. We felt something was needed, and that’s why we wanted to offer something giving a quicker answer. We are aware that football is different [from other sports] and making a decision faster was important, and that’s why we worked in this direction.”
How will Semi-Automated Offside Technology work?
At the moment, VAR can only use broadcast cameras to make offside decisions. But with semi-automated offside technology, cameras will be set up on the roof of the stadium. They will be able to track all 22 players to calculate their exact position on the pitch. There will be 29 data points on each player to cover all possible limbs and extremities that could be offside.
Also, the official World Cup match ball, the Adidas “Al Rihla,” will be fitted with a sensor that sends data 500 times a second. This means it can detect the exact moment the ball was played for the offside decision – far more accurate than the conventional camera frames (limited to 50 frames a second).
“We will implement in each World Cup stadium, 12 dedicated optical tracking cameras,” Holzmuller said. “All these cameras are working together, and 100 percent synchronised. In addition to that, the official match ball will have a connected ball technology. A new Adidas suspension system houses a 500 hertz IMU [inertial measurement unit] sensor in the centre of the ball.
“This information is transmitted via antennas inside the stadium to the video operations room. In order that the system can detect precisely the offside position, the optical tracking system is collecting 29 data points, and this will happen 50 times per second.
“The IMU sensor inside the ball will provide a ball data stream than is nothing more than the acceleration data of the ball in multiple axis. We will get an automated detection of a very accurate kick point, which is especially important in very close and very tight offside situations.
“We are combining the different data sets by applying Artificial Intelligence, and this automated alert is then appearing on a timeline inside the video operations room. This is happening immediately, within a few seconds. But then of course in addition there’s the manual validation process by the video match officials to make sure that the data and everything is correct.”