Gunnarsson (undisclosed) partnered with Jake Walman at Wednesday's scrimmage, Lou Korac of NHL.com reports.
Gunnarsson is entering the final year of his contract, and it appears he won't be a nightly player for the Blues this year. Torey Krug, Marco Scandella, Justin Faulk, Vince Dunn and Colton Parayko are fixtures on the blue line, so Gunnarsson likely will rotate in with Bortuzzo in the shortened 56-game campaign.