Harlequins captain Chris Robshaw insists competition for places will be intense as they look to regain their Aviva Premiership title this season.
The 2011/12 champions relinquished their crown after a play-off semi-final defeat to Grand Final winners Leicester last season, and director of rugby Conor O'Shea has added extra strength to his squad over the summer.
Experienced trio Paul Doran Jones, Nick Kennedy and Paul Sackey have all been recruited by O'Shea in the off-season, and England skipper Robshaw believes the depth of talent at Quins means nobody is guaranteed a first-team place.
"You always have to look over your shoulder for new guys but that's what's great for the squad, it makes you a better player. If you start to coast you potentially get a bit lazy," said Robshaw.
"We use the A League and the LV= Cup in particular for a lot of those young guys and they showed exactly what they can do, to win both those tournaments was incredible and great for the club, it really shows the youth coming through.
"In the U20 World Cup, Jack Clifford and Harry Sloan performed extremely well and that's what you want. My year was that of Mike Brown, George Robson and you look at the years coming through now - there are handfuls of them."
Harlequins take on Wasps in their season opener at Twickenham on Saturday, and Robshaw is hoping for a more routine victory over their London rivals than their remarkable battle last year.
Quins roared back from 40-13 down to snatch a dramatic 42-40 victory with a last-minute penalty from Nick Evans, and Robshaw added: "Last year against Wasps was a little bit too much for the heart! But hopefully we can start a bit better. We have to make sure we're on the money.
"We have experienced what it is to be both sides of it now - to be defending the title and hunting it - and what it takes when you don't play well and you grind out results.
"That's something that comes from a bit of maturity and experience. Hopefully the squad is really starting to show that."