Mike Smith was half a period away from shutting out the Calgary Flames in Game 3 of the Edmonton Oilers' second-round Stanley Cup playoff series on Sunday.

And then came Milan Lucic.

Calgary trailed 4-0 midway through the third period when Lucic barreled into Smith while he played the puck behind Edmonton's net.

The collision was bad enough that NHL concussion spotters forced Smith out of the game to be evaluated. Smith was clearly irate about the decision, arguing fruitlessly with referees to stay in the crease. He did finally exit, replaced by backup Mikko Koskinen.

Lucic was assessed a five-minute penalty for charging and a game misconduct -- an automatic ejection -- for his part in the incident. But following the Flames' eventual 4-1 road loss that put Edmonton up 2-1 in the series, Calgary coach Darryl Sutter said he believed Lucic made a real effort to cushion the blow.

"They called [it a penalty for] charging, correct? Can you imagine if Looch did charge?" Sutter said. "What would have happened there? He actually tried to slow it down a little bit, I think. But it is what it is, it's the score [being 4-0] and who it was and that's what they called."

Smith also was admittedly confused about how that play was assessed.

"I don't think my head hit anything," he said. "My helmet came off, but I didn't get hit in the head. I didn't really know what happened. I was playing the puck, and the next thing I know, I'm getting buried into the end boards."

Before that, the veteran goaltender was finally in his element after a tough start to the Battle of Alberta. Smith was pulled from Game 1 after allowing three goals on nine shots in a 9-6 Oilers loss. He rebounded well with a 37-save showing in a 5-3 Game 2 victory, and he had made 28 saves on Sunday prior to being removed.

Koskinen spent only 4:19 in net -- and didn't face a single shot -- before Smith returned to a standing ovation. He did give up one goal, to Oliver Kylington, after coming back but was otherwise pristine.

On any other night, Smith's coming and going might have sufficed for goalie drama. Not so in Game 3. By its end, all four goalies from both teams had made appearances.

At the time of Smith's departure, Calgary's Jacob Markstrom had already been pulled after giving up four goals -- all in the second period -- on 34 shots (.882 save percentage). Flames backup Dan Vladar was in net for the third.

It's been a rocky series overall for Markstrom, who had allowed 11 goals through Games 1 and 2 (.838 SV%). Markstrom's sensational regular season (.922 SV%, 2.22 goals against average) made him a finalist for the Vezina Trophy, and he looked the part in the first period of Game 3, making all 21 stops.

Edmonton opened the floodgates just 52 seconds into the second period, though. Zach Hyman was on the board first, and Evander Kane then scored a natural hat trick in only six minutes. Leon Draisaitl had four points on the night. Connor McDavid had three.

Oilers coach Jay Woodcroft appeared to take a dig at Sutter's management of Markstrom after Game 3, pointing out that while Smith was limited by injuries in the regular season, Markstrom had played a lot of hockey.

"Mike Smith only played 28 games in the regular season and 10 in the playoffs," Woodcroft said. "He's 38 and in midseason form. He didn't play 63 games [during] the season and have the wear and tear that comes with that."

Game 4 is Tuesday.