Graves and Day will be worse on the ice in the NHL (right now at least) than Staal and Holden. Clendening is a borderline NHL-er who several teams moved on from but somehow people think he will hold his own. Basically Matt Gilroy
Graves would be better than Staal right now, which isn't hard to do.
Staal would struggle in the AHL too. He couldn't keep up against the Pens AHL squad in the last game of the season which was the reddest of red flags in a season where he planted a bunch of them. He's been abysmal during the whole playoff run, There isn't a team out there who made the playoffs who has iced a defenseman worse than Staal.
Clendo is better than Holden. Say what you want about his match ups, he performed exceptionally well with what he was given, and he was great with Skjei too. Nashville is using a 3rd pair of Yannik Weber and Matt Irwin, those are guys who are about on the same level as Clendo. They're doing just fine.
Day isn't close to NHL ready, but I'd rather have one guy in there who isn't an NHL level player than 2 in G and Staal.