But having edged his close friend for a starting berth at the start of the season 50-cap All Black and World Cup winner Cowan pitched up in October to aide their Aviva Premiership charge.
Robson - an England U20 international - has no qualms though and claims his own game has come on leaps and bounds with the help of Cowan's wise words.
Indeed, having played just 35 minutes fewer in the Aviva Premiership this term than Cowan, Robson insists he couldn't be in a better place to learn his trade.
"I'm really happy with how things are going, I've been getting a bit of game time this season and learning a lot from Jimmy," said Robson.
"I was pretty happy when he signed this summer, I'm obviously still young and got a lot of learning still to do, and to be training with someone like Jimmy who has been there and done it is pretty surreal but also great. He's a great guy to have around the place as well.
"I tend to watch what he does and try to apply it to my game, but he also talks to me as well, it's a bit of both.
"It's really important for my development, the last few weeks and months have been a great learning curve.
"I'm quite happy if I'm on the bench, I try to make an impact as and when I do come on. I'm excited by the challenge Jimmy poses, it can only help my development and that of the club as well."
Robson played a starring role in Gloucester's 31-26 win in the Amlin Challenge Cup against Bordeaux-Bègleson Friday - a victory that secured their passage into the quarter-finals.
But with Mont de Marsan lying in wait on Saturday, and a home tie in the last eight still up for grabs, Robson has warned his teammates to keep their foot on the gas.
"It was a good win over in France [against Bordeaux], we've booked a quarter-final spot but we want that home tie now," he added.
"I think getting a tie at home could help a lot, but we've got a really tough game coming up on Saturday [against Mont de Marsan], we can't get ahead of ourselves.
"It's going to be a massively physical challenge, they're your typical tough French side, so we're not looking much further than them at the moment.
"We're disappointed not to be in the Heineken Cup, but the Amlin is still a good competition, very competitive, and we think we can win it."
You can buy tickets here to see Robson and Gloucester maintain their charge for silverware this season