Ehn, 22, has played in 44 games with the Wings this season, recording two goals and five assists as an even player.
Mantha, 24, is in the midst of a four-game point streak in which he has two goals and five assists.
Mantha is also third on the team in goals with 16, behind Dylan Larkin's 26 and Andreas Athanasiou's 22.
Blashill also said Larkin and Mike Green, who both missed practice Thursday, are expected to play.
COYOTES HOWLING: The Arizona Coyotes are one of the hotter teams in the league.
Since their 5-0 victory over the New York Rangers on Jan. 6, the Coyotes are 14-7-2.
They have won five straight games and eight of their last 10.
"I think Tocch's (Coyotes coach Rick Tocchet) done a real good job with that team," Blashill said Friday in Detroit. "Last year they had a real tough start and it buried them a little bit but their second half was very good once they started getting real good goaltending. The beginning part of the year, they just didn't get very good goaltending. I thought once they started to get way better goaltending, they were a very, very good team the second half of the year. They work up front, they've got a pretty good D corps, they've got some depth. They've got a good combination of some guys like Derek Stepan, who's been a real good pro, although I think he got hurt (the other) night, and some younger guys like (Clayton) Keller and (Alex) Galchenyuk and that so you've got some talent infused with some good, veteran mix. Richardson's having a heck of a year and then (Darcy) Kuemper's been great here lately.
"Like anything in this league, when your goalie gets hot, it helps you a ton and their goalie's been hot. Then I think the fact that in the West, all those teams see light. That last playoff spot's attainable for so many teams because of where the point total's at that they see light at the end of the tunnel. It keeps you going."
In the new year, Kuemper is 14-3-3 with a 2.31 goals-against average and .925 save percentage.
Kuemper's 14 victories in 2019 rank second in the NHL.
The Coyotes also benefit from having the league's top penalty kill at 85.9 percent.
"Pressure. Early pressure, especially," Blashill said. "When you get set up on them they're not a whole lot different than a whole lot of other teams. They give up some seam plays. Usually, when you give up seam plays you're in a tough spot on the kill. What they do do is they pressure up the ice and they pressure in the zone and they don't allow you to have many easy set-ups.
"They also have some elite premier shot-blockers on the back end. (Niklas) Hjalmasson's been on the best for a long time. I think (Jordan) Oesterle does a real good job blocking shots. When you do get into the flanks or you are able to break them down a little bit they seem to block a lot of shots."
However, the Coyotes lost Stepan, one of their top penalty killers, for the remainder of the regular season with a lower-body injury.