The performance of Desert Jeuney in the Pakenham Cup will convince his trainer Nigel Blackiston whether to keep him to longer races.

Blackiston harbours doubts the seven-year-old will run a strong 2500m in Saturday's Cup, his first shot at a staying trip in more than 2-1/2 years.

The trainer said as Desert Jeuney was ageing, now was the time to give him another distance test.

"I'm still not 100 per cent convinced he's a stayer but we've come this far now and he's fit and well so we might as well give it a try," Blackiston said.

Whlle he is yet to win beyond 2000 metres, Desert Jeuneys's breeding says he should. He is by Irish Derby winner Desert King out of Preps, a mare by Melbourne Cup winner Jeune.

The last time Desert Jeuney contested a staying race was when eighth behind The Offer in the 2014 Sydney Cup.

Desert Jeuney has raced at 2400m, or further, three times with a best finish of fifth in the Chairman's Handicap in the lead-up to his Sydney Cup performance.

All Desert Jeuney's staying performances have been on rain-affected tracks while his best efforts have been on firmer surfaces.

While Blackiston may not be convinced about Desert Jeuney's staying prowess, the gelding did show Group One potential when kept to shorter trips.

He ran third in the Toorak Handicap at Caulfield in 2014 and followed that with a third in the Waterford Crystal Mile at Moonee Valley.

"He was kept a little bit fresher and that seemed to help him back then," Blackiston said.

"But now as he's getting a little bit older he's shown that he possibly will appreciate a little more distance."

Desert Jeuney has been to the new Pakenham track once, winning over 2000m last year while he was also successful on the old Pakenham lay-out, winning on debut in 2013.

He enters Saturday's race off a last-start seventh behind Pilote D'essai in the Ballarat Cup in which he was a victim of a wide draw and a track favouring on-pace horses.

"Hopefully he draws a nice barrier for a change," Blackiston said.

"He had barrier 16 last time and we had to go back and it was an on-pace track.

"He finished it off nicely so it warranted heading towards Pakenham now."