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 the Hasseroder right-hander.
Engel rejoined the track and tapped Rast’s M4 GT3, although it was Engel who took the worst of the hit as his car slewed sideways on the short dash towards the next left-hander.
The stewards deemed Rast’s initial move that forced Engel off the track was 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.”
The contact dealt damage to Engel’s exhaust, costing him straightline speed in comparison to Landgraf team-mate Jusuf Owega.
A long-lap penalty for a pitstop infringement, which also caused erstwhile race leader Thomas Preining to lose a likely victory, eventually left Engel a disappointing 14th at the flag after he'd taken 13th from Saturday's season opener.
On his part, Rast played down the clash as “just normal racing”, saying Engel 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 manoeuvres. 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, which meant his fifth place finish in race one was Rast's only score from the weekend.
The points standings are led by Toksport WRT Porsche driver Tim Heinemann, the series rookie finishing second in both races to Franck Perera (SSR Lamborghini) and his own team-mate Christian Engelhart.
