Sherrif Tiraspol witnessed disturbing scenes when winger Adama Traore went down clutching his chest in Wednesday night's clash with Real Madrid.
The Mali attacker committed to a 50/50 challenge on the touchline with Real Madrid's Nacho Fernandez and when the ball went out of play Traore appeared under duress.
Traore, 26, turned to walk away from the ball, which had gone out for a throw-in, in the 77th minute when he immediately became uncomfortable, clutching his chest before slumping to the turf.
He remained breathing throughout but after a few seconds of lying on the ground in distress the Moldovan side's medics raced on to help.
Medics immediately looked to use smelling salts to activate his senses but he was not reacting strongly too them.
He was seen shaking his head in responses to questions by the medics and was eventually raised to a sitting position before being helped off the field and back to the dressing room.
The Moldovan side have yet to detail the reasons behind why Traore was suffering from chest pains.
Concern for Traore comes soon after Barcelona striker Sergio Aguero was diagnosed with cardiac arrhythmia after he was forced off with chest pains in their 1-1 draw against Alaves.
The Catalan giants have since ruled the 33-year-old Argentine out of action for the three months as a period of rest once extensive medical tests had been carried out.
Aguero insisted he was in 'good spirits to face the recovery', tweeting: 'I am fine and in good spirits to face the recovery process.
'I want to thank everyone for so many messages of support and affection that make my heart stronger today.'
Earlier this week Sheffield United midfielder John Fleck collapsed on the pitch during his side's Championship fixture with Reading on Tuesday night.
The Blades were leading 1-0 thanks to Jayden Bogle's 56th-minute strike when Fleck collapsed on the pitch in the second-half.
His team-mates immediately called for medical assistance and the 30-year-old received 10 minutes of urgent treatment on the pitch at the Madejski Stadium before being transported to Royal Berkshire Hospital.
After remaining conscious in hospital for around 12 hours, Fleck was released on Wednesday morning and headed back to Sheffield and will be monitored by the club closely after speaking clearly to the club, medics and his family.
Sportsmail produced a special report on the issue with one in every 260 players holding a life-threatening heart issue.
Five months ago at Euro 2020 there was the harrowing collapse of Denmark midfielder Christian Eriksen and last month Icelandic midfielder Emil Palsson required resuscitation. Both suffered cardiac arrests on the pitch.
