Gambrell (concussion) was placed on waivers Sunday, according to Chris Johnston of TSN.
Gambrell "won't be available for a while" due to a concussion, Terry Koshan of The Toronto Sun reports.
Gambrell inked a one-year, $775,000 contract with Toronto on Monday, per PuckPedia.
Gambrell recorded an assist in Saturday's 7-4 win over the Lightning.
Gambrell scored his second goal of the season in Tuesday's 2-1 loss to the Bruins.
Gambrell earned an assist against the Red Wings on Monday.
Gambrell logged just 10:24 of ice time in Sunday's 4-2 loss to Minnesota in which he recorded one shot, one hit and two blocks.
Gambrell secured a one-year, $950,000 contract from the Senators on Wednesday.
Gambrell (illness) is expected to draw back into the lineup for Saturday's game versus the Rangers, TSN 1200 Ottawa reports.
Gambrell found twine in Saturday's 4-3 shootout loss to the Panthers.