The 30-year-old left shot was playing his offside for the Rangers, matched on the team's top pairing with captain Ryan McDonagh. Where - or when - he fits into the lineup with the Bruins is still to be determined.
Now with nine healthy bodies, Boston's back end is fully stacked. Kevan Miller, who has missed the last nine games with an upper-body injury, has been ready to rejoin the lineup since last weekend, but has not been able to break back in due to the strong play of Grzelcyk and McQuaid on the Bruins' bottom pairing.
"I don't know when [Holden] will go in, to be honest with you. Could be [Saturday] or Sunday or after that," said Bruins coach Bruce Cassidy, while also leaving open the possibility that Miller returns on Saturday against the Leafs.
"We've liked the seven guys we've used over the last two months. We can't forget about that and I have loyalty to the guys that got us here. That's a conversation that we have again internally.
"We've talked to him about it directly, told him that's the situation. We've generally played the guys that deserve to play this year. Once he's in, it's his job to stay in and that's about it."
Holden has played 356 games over seven NHL seasons for Columbus, Colorado, and New York. The 6-foot-4, 214-pound veteran, who set career highs in goals (11) and points (34) last season with the Rangers, has played in nearly every situation during his career and has been a major contributor on the penalty kill.
"He had [11] goals last year," said Cassidy. "I think he's predominantly a 5-on-5 guy - more PK than power play. But clearly when you score [11] goals you've got some ability. He shoots the puck well. I do remember that from years ago [in the American League].
"I think he could add to the second [power play] unit when you're going with two D - usually it's Charlie [McAvoy] and [Zdeno Chara], it's been Grizz at times. If he's in there he can certainly add to that."