Dutch cyclist in the opening stage of the Tour of Poland in Katowice.
Groenewegen veered suddenly to the right, squeezing his rival into the security wall. Jakobsen somersaulted over the barriers before colliding with a race official.
Groenewegen went on to win the stage but was later disqualified with Jakobsen declared the winner.
Jakobsen was left fighting for his life and underwent a five-hour operation immediately after the accident.
Pawel Gruenpeter, deputy head of the hospital, on Thursday said his condition had improved but was still "serious but stable" as he was taken out of the coma.
Groenewegen on Thursday also apologised saying: "I can't find the words to describe how sorry I am for Fabio and the others who fell or were affected.
"I am thinking about him all the time," he wrote.
The Katowice prosecutor's office has opened an investigation into the accident.
Police have also gathered records of the crash, along with the bikes of the injured riders.
'Very dirty move'
Governing body UCI also said it "strongly condemns the dangerous behaviour of Dylan Groenewegen" and has referred the incident to a disciplinary panel.
Having turned professional in 2018 with Quick-Step, Jakobsen donned the Dutch champion's jersey in June last year.
The 24-year-old Trek-Segafredo rider dedicated his victory to the stricken Jakobsen.