It was difficult to separate a morose mood influenced by lack of first-team opportunities from what appeared to be a naturally withdrawn presence among team-mates.
For a player handed a treasured Football League opportunity at the age of 25, the attacking midfielder bore the demeanour of a tortured soul condemned to an excruciating existence.
It was impossible not to feel sympathy for this dejected figure condemned to patrol the training ground rather than the football pitch, such was his perpetual match-day inaction.
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Dennis was named in just three of Kenny Jackett’s final 20 squads of last season. What turned out to be his final Blues appearance arrived in a 2-0 FA Cup defeat at QPR in February 2019.
His misery was finally banished in August, long-time admirers Leyton Orient capturing the ex-Bromley man on a two-year deal for an undisclosed fee.
As ever among football supporters, his reputation rocketed during Blues inactivity.
Despite one fleeting substitute appearance in League One and a total of eight outings and one goal, a period of mourning marked his departure, amid many raised voices questioning the sanity of Jackett.
Still, Dennis’ fresh beginning has, as of yet, not made Pompey regret that decision.
Currently sidelined by a persistent knee injury, the 27-year-old has started seven League Two matches for Orient during a campaign in which he has largely failed to convince.
Despite an encouraging start, one of their much-vaunted summer recruits upon their Football League return is once again enduring a season of frustration.
‘There were high hopes when Dennis was signed, a lot of people had seen him play for Bromley in the past and expected a player who could create and score,’ said Jacob Ranson, sports reporter for the East London Advertiser and Newham Recorder.
‘This represented a really good signing, especially dropping down from a big club like Pompey, who appeared reluctant to let him go.
‘However, although he looked quite bright in the opening month, he has generally only shown glimpses. We’ve not seen the best of him.
‘I thought he was going to be quite a good signing when he was announced, Pompey fans said they didn’t want to see him leave, but he has struggled to stay in the team.
‘There’s quite a lot of competition in the areas he plays in, but mainly Dennis has been in and out of the squad due to injury.
‘The club have said he has been due to return from injury on several occasions, only to collect another knock to rule him out once more. Once fit, though, he will have to work his way back in.
‘Dennis has not been used as a number 10 since arriving, earlier in the season he was on the right or left of the attacking three in a 4-3-3 system.
‘While he has been out injured, results have recently picked up, with James Dayton and Jordan Maguire-Drew playing in those attacking midfield roles – and they are stern competition.
‘Every time he appears ready to come back to challenge, injury happens again, most recently last week. It has been difficult for Dennis.’
The former Pompey man has featured for just seven minutes in Orient’s last 16 matches in all competitions.
During that period, he has twice been an unused substitute, reflecting ongoing injury battles which have devastated availability to head coach Ross Embleton.
It was Embleton who recruited Dennis, albeit serving in an interim role following the tragic death of manager Justin Edinburgh in June having returned the club to the Football League.
The attacker had long been admired by the late Edinburgh and his management team, with Orient declaring their interest in his services early last summer.
However, they were initially rebuffed by Jackett, who was impressed by Dennis during his return to pre-season training, at one point earmarking him for a regular number 10 role with the Blues.
Indeed, the former Watford trainee was handed the position for the opening pre-season friendly at Irish side UCD, registering two goals and two assists during his 45 minutes on pitch in the crushing 11-0 success.
There was also a start ahead of Andy Cannon and Brett Pitman at the Hawks in the second match of the summer, featuring for 70 minutes in the 2-1 victory.
Dennis never played for Pompey again.
Ranson added: ‘Having lost Macauley Bonne and Josh Koroma following promotion, the attacking area required strengthening. Orient brought in Conor Wilkinson, Lee Angol and, of course, Dennis.
‘He came off the bench at half-time against Mansfield in August and grabbed two assists in a 3-2 win, while scored his maiden goal at Exeter the following month.
‘Dennis featured quite a bit in those first few months of the season, but hasn’t really played too much since, which is a shame.
‘He’s quite energetic and creative, likes to run at people and, in the early part of the campaign, looked to break into the box beyond the full-back. Then the team as a whole went into a bit of a downward spiral, not just Dennis.
‘Carl Fletcher came in as manager, it didn’t seem to work, and they pulled the trigger early rather than leaving it too long and becoming involved in a relegation battle, so Embleton became head coach again.
‘It has been a crazy one, a lot of chopping and changing trying to find some stability, but in the last month or so it has turned around and the team have started to pick up.
‘Unfortunately for Dennis, he hasn’t played at all during this run – and we’re still waiting for him to return from injury to show what he can do.’
In May 2018, Pompey gambled on two players costing minimal expense – Bromley’s Dennis and Derry City’s Ronan Curtis.
Today, Curtis is heading for Pompey Player of the Season honours with 13 goals, while earlier this month earned a fresh three-and-a-half year deal.
Meanwhile, with 21 appearances and two goals this term, Dennis still strives to bring a smile to the face of Orient supporters – and himself.