That gives them quite a bit more cap breathing room than if they had taken on Elliott too.
They really couldn't have taken on Elliott without telling Sekera to stop his conditioning stint. The NHL already granted a 2 game extension to the Oilers regarding Sekera's conditioning stint on the 14th, the Condors played last night and do again today.
The Oilers next game (after tonight) is Tuesday, they pretty much need to have cap space for Sekera by then. They currently need to shed just shy of 875k in AAV, had they taken Elliott back, they'd need to shed 3.55m in AAV.
So, by Monday morning, if they have not traded away at least $865,628 in AAV, they will have to waive someone (and demote them Tuesday), in order to have space to activate Sekera. Since they are carrying 8D and 13F on their roster, it is only logical that the move will involve a defenseman. Gravel only has a cap hit of 700k, which isn't enough. The most logical IMO is Petrovic, because he is most likely to be grabbed off waivers as a pending UFA. I cannot see anyone grabbing Benning or Manning off waivers with each having an additional year on their contracts.
edit: and literally as I typed this put the Oilers traded Spooner for Gagner