Having edged Neuville by a slender 2.6sec through the opener, championship leader Sébastien Ogier looked poised to pull clear of the pack as he made the most of the clean road surface offered by his starting position.
But the Frenchman came unstuck only a handful of kilometres into the following test, Stojdraga - Hartje, when he stopped to change a wheel after hitting a pothole with his Toyota GR Yaris. Team-mate Kalle Rovanperä, himself a previous Croatia winner, struck identical trouble at the very same location.
Ogier’s time loss elevated Neuville into the top spot and, although he felt his Hyundai i20 N’s set-up was hindering progress, the Belgian outpaced nearest challenger Elfyn Evans on all but one stage.
“It’s hard,” Neuville said. “We are trying different set-ups all the time, but I just can't get the right thing. It's very similar to Monte-Carlo where the chassis is moving a lot, and it makes the car very nervous. When it's a bit faster I am struggling to control the car."
Neuville was lucky to escape with minimal damage when he hit a hay bale chicane in SS2, while Evans was also counting his lucky stars after collecting a slow puncture on the final corner of the next stage.
"We had it just near the end, so I don't think it cost us too much," omitted the Toyota man. "It looks like we were quite lucky with that one."
M-Sport Ford’s Ott Tänak completed the podium only 6.1sec further back despite nursing a steering-related problem which began on the first road section of the day. A stall just a short distance into the opening stage also cost a handful of seconds.
Esapekka Lappi’s speed improved over the morning as he acclimatised to the dirty asphalt conditions. The Hyundai star trailed Tänak by 12.7sec at service with Takamoto Katsuta another 15.3sec behind in a Toyota.
A trouble-free morning saw Pierre-Louis Loubet hold sixth in his Puma ahead of the recovering Ogier, who languished 1min 27.1sec back from the lead despite winning three out of four stages.
WRC2 leader Yohan Rossel was eighth and held a commanding 29.7sec advantage over Nikolay Gryazin, second in the category. Nicolas Ciamin completed the early top 10.
Finland
Italy
Hungary