Schubert BMW driver Rast was fighting with Engel for ninth position on the second lap of the race when he pushed his Landgraf Mercedes rival wide and over the grass at the exit of Hasseroder.
Engel rejoined the track uncontrollably and tapped Rast’s BMW, although it was Engel who came off worse, with the rear of his Mercedes stepping out on the short dash towards the next left-hander.
The stewards deemed Rast’s initial move that forced Engel off the track to be too aggressive and asked the three-time champion to hand back the position, which he duly did to reinstate the Mercedes driver into ninth place.
But Engel was still furious at Rast, having feared the incident could have forced him into an early retirement from the race.
"I felt like Rene's punching bag,” he said in a TV interview. “He drove into my car four or five times. I don't know what he had for breakfast this morning.
"I thought I was gone. I just tried to save the car somehow and somehow I succeeded.
“I almost lost the car and almost hit it. Pretty unnecessary for me at this early stage of the year.”
Big save by @MaroEngel ! @ReneRastRacing #DTM2023
— DTM (@DTM) May 28, 2023
Watch live here: https://t.co/H4v7VeONmF pic.twitter.com/SWqyr5vWyi
The contact dealt damage to Engel’s exhaust, costing him 2-3km/h in top speed in comparison to Landgraf team-mate Jusuf Owega.
A long-lap penalty for a pitstop infringement eventually left him a disappointing 14th at the flag, six places behind DTM rookie Owega.
For his part, Rast played down the clash as “just normal racing”, saying Engel himself had pushed his team-mate Sheldon van der Linde off the track in Saturday’s opening race of the weekend.
"I spoke to Sheldon before the race and told me that Maro was super aggressive on Saturday and also pushed him off the track two or three times,” said the 36-year-old.
"I think that in DTM we want to see hard maneuvers. We don't want soft drivers who don't fight each other. That's what the fans want to see."
Rast would go on to retire from the race after the right-rear tyre rim of his BMW suddenly broke at Turn 1, leaving him beached in the gravel. It is unclear if the incident with Engel was the root cause of the issue.