Dennis (BMC) has retained the overall lead with a one-second advantage over defending champion Tom Dumoulin (Sunweb) after stage four of the Giro d'Italia.
After three opening days in Israel and a rest day, the Giro finally reached Italian soil on Tuesday, with Tim Wellens (Lotto Fix-All) living up to expectations when he won the 202km treacherous ride from Catania to Caltagirone in Sicily with a punchy finish.
But Dennis managed to stay close to leaders to ensure he kept hold of the pink jersey.
"Of course I want to stay in the front," he said. "It's great to keep the jersey for a little bit longer, the team did everything possible to put me in that position. It was a little bit stressed, but not so much.
"It was a question of staying out of trouble from the last 10 kilometres until the bottom of the last climb. We were hoping that if I was feeling good, I could try and take the sprint but with 250 to go, I knew it wasn't possible, so I just made sure there were no big gaps.
"It's pretty common that I've lost the leader's jersey after one day in other Grand Tours. To retain the Maglia Rosa today is big for me."
Wellens was on the right end of a late split and he sustained his effort on an 800 metres climb up an average gradient of almost 10 per cent to the finish line.
He beat Michael Woods (EF Education First-Drapac/Cannondale), who was seconds ahead of Enrico Bataglin (LottoNL-Jumbo).
“I saw that Battaglin accelerated with 250 metres to go. I took his wheel and passed him 200 metres from the finish. Then it was just the case of pedalling as hard as I could to make it to the finish. I wasn’t sure though until I crossed the line," Wellens said.
“The victory of today is very different to my previous Giro stage victory in Roccaraso. Two years ago, I had a lot more time to celebrate. Today, I was the best of a group including all the big favourites. Actually, this victory gives me a better feeling than two years ago.
“The whole team did a great job today. We took the initiative together with BMC to control the breakaway. We stayed in the front during the whole day, but there was some panic when UAE accelerated and tried to drop some riders. Adam Hansen and Tosh Van der Sande delivered an incredible effort today. The pace was so high that it caused a split in the peloton when we began the final ascent. The team was a great part of the victory today.
“We came to the Giro to win a stage. That sounds obvious but it is not easy to fulfil those expectations. We can continue the Giro now with a lot less stress, having already won a stage. I am sure other opportunities will follow, not only for me but also for other guys in the team. But for now, it is nice to have that first stage win secured.”
Chris Froome finished 21 seconds behind Wellens, pushing the four-time Tour de France champion down to 20th overall and 55 seconds behind Dennis.
Froome, who is attempting to win his third straight Grand Tour, already struggled in the opening time trial after a training crash.
"I wasn't in great position getting into the (finishing) climb," Froome said. "But I'm getting better and better each day after the crash."
José Gonçalves (Katusha-Alpecin), third overall at the start of the stage, suffered a mechanical in the finale and dropped out of the top 10.
There are two more difficult stages in Sicily, including an arduous ascent up Mount Etna on Thursday, before the race heads over to mainland Italy and climbs up the peninsula to the defining climbs in the Alps.