With Anton Stralman already nursing an injury, another Lightning defenseman could miss time, too.Ryan McDonagh is day-to-day with an upper-body injury, the Lightning announced Friday.McDonagh will travel with the team, though. The Lightning kicks off a three-game road trip against the Panthers on Saturday.McDonagh left the game against Buffalo in the first period under his own power after Buffalo captain Jack Eichel shoved him into the boards. Eichel hit him at an awkward angle because McDonagh was already leaning forward. He went head first into the boards and was slow to get up while a scrum erupted around him.It forced the Lightning to play the rest of the game with five defensemen.“You could see it probably wore a little bit on us a bit,” assistant coach Derek Lalonde said Friday. “Their best push was in the middle of the second period.” When McDonagh left the game, the Lightning lost a skater who plays significant minutes. He averages 22:04 per game, trailing only Stralman (22:25) and Victor Hedman (22:16).McDonagh also plays a vital role on special teams.“When our penalty kill was No. 1 in the league, (McDonagh and Stralman) were our top two guys killing the first 1:15 out,” Lalonde said. “And not only does McDonagh thrive in those minutes, he wants those minutes.” If McDonagh misses time, Slater Koekkoek will likely fill his spot in the top six. Koekkoek was a healthy scratch on Thursday, but he has played in nine games this season.“His best asset is he can skate,” Lalonde said. “That’s why I think when he comes in, it is seamless because of his ability to skate. He skates and he will get right in and be a good asset for us.”Joining him in the group of six healthy defensemen: Dan Girardi, Hedman, Mikhail Sergachev, Erik Cernak and Braydon Coburn.The re-shuffled d-pairings in Friday's practice:Hedman-GirardiKoekkoek-CernakCoburn-Sergachev“As long as you do your job properly, it’s the same game plan no matter who is out there,” Girardi said. “We still have to be good defensively. It doesn’t really matter who is out there with you.” Other absences from Friday's practice: •J.T. Miller missed practice for dental work. In the game against Buffalo, he was the recipient of a hit via a high stick. It drew some blood, resulting in a four-minute penalty.• Adam Erne missed practice because of an illness. He will travel with the team.• Ryan Callahan did not practice because he was taking part in a treatment day.