The following season he found the target in his first five games, a period that coincided with the birth of his son, Alfie. In both his professional and personal lives, Russell could not have been more content. The onset of his depression, then, had no identifiable trigger. The black dog had barked for no obvious reason.
Russell was 28 years old at the time, with no history of mental health issues in his "loving, close family". Soon, a period of feeling a bit down would grow to the point where he wasn't eating, wasn't taking the medication prescribed for him, and had little inclination to do anything at all. At training, instead of enjoying the usual camaraderie of the dressing room, Russell would hide in the toilets, desperately seeking any form of sanctuary.
There were days when he could barely lift his head off the pillow, others when he went to sleep and hoped he wouldn't wake up at all. There were anxiety attacks, and other times when he just felt really low. It was the most challenging and stressful period in his life. "I hit rock bottom," he admits now with admirable candour.
Physical knocks and strains are an occupational hazard for professional sportsmen and women but the prospect of chinks in their mental armour is not something many are prepared for. Such is the nature of their profession that the instinct is to show no sign of weakness, to give the opposition no demonstration that all is not well.
It takes a lot of courage, then, for one to reveal they are struggling mentally. Russell admitted it first to himself, then to his family, his doctor, employers, the players' union, and now to the public in a new film produced by PFA Scotland entitled "Mind Games - Mental Health in Scottish Football". He hopes others will benefit from his revelations.
"It wasn't something I had dealt with before and nobody in my family had experienced something like that," said the Queen of the South striker prior to yesterday's premiere screening. "There weren't any signs beforehand. I had a good season with Livingston, and my son was born so I was in a good place when it first started. There's nothing to explain it. I was just really low. I didn't want to do anything. I had a job to play football and I was struggling to do that. I had to take time off."
Tackling his problems head-on proved a cathartic experience. The macho world of football can seem an unforgiving place but instead Russell found sympathetic managers and tolerant team-mates.
"It's been great the way people have reacted to me - especially from within the dressing room," he added. "The majority of them know that I have been suffering so it helps me and it probably helps them as well. It makes it a lot easier.
"I suffer day-to-day but I have more good days than bad days now and that has been down to a lot of help and talking to a lot of people. I don't know if I will totally get over it but there are more good days than bad. I've got a two-year-old son, Alfie, and he's my inspiration. If I'm feeling low then I just think that I'm doing everything for him."
Football was not always so accommodating. Tony Higgins' current work with PFA Scotland and FIFPro, the international players' union, brings him into close contact with the many programmes designed to support the modern footballer. It is a far cry from his playing days of old when anyone confessing to feeling low would have been laughed out the dressing room and carpeted by the manager. The extent to which depression can take hold was laid bare when Erich Schaedler, a team-mate of Higgins' at Hibernian, took his own life.
"Erich was always either very high or quite quiet, he seemed to oscillate between the two," recalled Higgins. "There are many theories been put forward since then about his condition. The game then wouldn't have recognised that. People would just have thought he was acting oddly. Iain talks about the importance of the camaraderie in the dressing room, and that they recognise what he's dealing with.
"In the bad old days that would never have happened. Erich could have been stigmatised just for exposing himself."
Now there are support mechanisms in place, something Neil Lennon, the Celtic manager and another who has suffered with depression at different times, acknowledged. "Football is a macho-dominated environment where people are worried about coming forward," he says in the film.
"I notice that some of my younger players, in particular, go from being outgoing to being very shy and introverted. The door is always open for them, obviously. Because, once you've experienced it, you can help others by passing on your experience and telling them it'll be all right.
"The best thing when you have depression is to talk to someone about it. They can explain that you're okay, that you are going through a bad period because of this illness - but you will get better. That gives a lot of people reassurance."