Leinster head coach Leo Cullen says Johnny Sexton's summer off has the potential to prolong his career even further.

The 36-year-old looked in tip-top form during his 40 minutes for Leinster in their 40-21 pre-season friendly win against Premiership champions Harlequins in front of nearly 10,000 fans at the Aviva Stadium.

Sexton was stood down following their Heineken Champions Cup quarter-final win against Exeter in April, while he failed to make Warren Gatland's British and Irish Lions squad, before being rested for Ireland's summer tests against Japan and the USA.

As a result of that layoff, he and fellow out-half Ross Byrne have been available to Cullen for all of Leinster's pre-season training, when usually the pair's Test commitments would see their arrival into the squad delayed.

Sexton scored a try and was centrally involved in two others during his eventful first half at the Aviva, and Cullen says the out-half's summer off could prove to be a benefit for both province and player.

"Really pleasing for Johnny just to get back out there," Cullen said.

"It's been a decent lay-off for him so he's nice and fresh which is good, like a bit of a sabbatical, time out for him, and add a bit more time onto his career which would be great.

"He led the guys well over the last couple of weeks and it's great to see him back out there, so much experience that he brings to the team. A positive 40 minutes for him and I thought Ross (Byrne) came in and controlled the game well in the second half which is a bit more challenging because there are so many changes in personnel and guys moving around particularly in the backline.

"Between the two of them they’ve been excellent over the course of pre-season. It’s been a real advantage having them around, we’ve been lucky that’s been the case," he added.

Last week, Sexton spoke of his frustration during his vacant summer, having to watch on as the British and Irish Lions were beaten 2-1 by South Africa.

And asked if the two-time Lion had returned to pre-season training with a new determination, Cullen joked that Sexton has never needed external motivation.

"Hopefully he’s calmed down at his age, he’s fired-up enough! He’s been great (since returning)," he laughed.

"We’re all gutted when players don’t get selected. There’s some guys that you’d love to have seen them away with the Lions.

"There were a few guys I thought were unlucky from our group, but we’re the beneficiaries of that because we have the likes of Johnny and a few other players around for pre-season, so it’s hugely positive for us, and for some of the young guys just to be around someone of Johnny’s level of intellect and level of experience in the game, it’s a great learning for those guys day-to-day.

"It’s been great just to have Johnny back out and playing, it’s a start, 40 minutes and hopefully we can build on that from here," Cullen added.

Meanwhile, Cullen allayed fears over the neck injury suffered by full-back Chris Cosgrave.

The Ireland U20 international was brought from the field on a medical cart following a lengthy period of treatment on the pitch, but Cullen says the extra care was precautionary.

"Yeah Chris is OK," Cullen said.

"I think when you see the cart come on everything gets a bit nervous, but he's OK. It was more to his neck, so his neck was stiff, but he’s OK there in the dressing room," he added.