Sunderland injury news: Key update on ex-Tottenham Hotspur defender
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Cirkin, a star performer through the opening seven games of the Championship campaign, missed Sunderland's most recent away games with a hamstring problem.
In his place Aji Alese made his full league debut and thrived, scoring his first senior goal in the 2-2 draw with Watford at Vicarage Road.
Speaking to safc.com, Mowbray welcomed growing competition in this part of the pitch.
However, it is not at this stage clear whether the Sunderland head coach will have a fit striker to call upon, with Ellis Simms continuing his recovery from a foot problem.
"Dennis Cirkin was back on the grass today [Monday] which was great," Mowbray said.
"There is competition because Aji Alese’s performance, in the couple of games he’s played, has been fantastic. It’s all encouraging at the moment.
“Ellis [Simms] is progressing and will hopefully be a bit closer – we’ll have to wait and see.
“We need to deepen the squad off when we can by Ross [Stewart] and Ellis [Simms] getting fit but also big Dan Ballard and Niall Huggins, players that can make the squad more competitive with everybody fighting for their place.”
Mowbray also warned that he will have to tread carefully with Jewison Bennette, who followed his equaliser at Watford with a brace for Costa Rica against South Korea.
"The internationals were away - the new lads have been away - Abdoullah Ba was away in France and Jewison was away in Seoul in South Korea, still is and won't be back until training on Friday," Mowbray said.
"I think he gets back on Thursday night, so it's difficult to integrate them into a team when they've been halfway around the world.
"But, I'd have to say Jewi has had a massive impact. The goal he scored at Watford and then he's been away with his country and scored a couple of goals as well so he'll come back on a high and we've got to try and utilise things like that.
"Balance it off against a guy who's been halfway around the world with jet lag etc coming back."