Glen Boss believes an apparent lack of depth among Australia's weight-for-age middle distance horses can help create spring opportunities for Shamrocker, a prized carnival ride for the leading jockey.Despite his reservations about the strength of the form out of last season's three-year-old classics, Boss says Shamrocker is well placed to add a major spring race to a Group One tally which already includes an Australian Guineas win and an AJC Australian Derby triumph."There looks like there is a

Glen Boss believes an apparent lack of depth among Australia's weight-for-age middle distance horses can help create spring opportunities for Shamrocker, a prized carnival ride for the leading jockey.

Despite his reservations about the strength of the form out of last season's three-year-old classics, Boss says Shamrocker is well placed to add a major spring race to a Group One tally which already includes an Australian Guineas win and an AJC Australian Derby triumph.

"There looks like there is a void up the top for a horse who might be a genuine weight-for-age (star)," Boss said.

"You've (still) got to see them come out and do it and hopefully she can make that transition to weight-for-age.

"And she's doing everything on the track off a spell with the gallops she's had to indicate she is going nowhere but forward."

There was been no bigger loss to Australian racing last season than the departure for Ireland of So You Think, the galloper who was afforded superstar status after winning his second Cox Plate.

The fact So You Think beat Zipping, now a 10-year-old, in the 2010 Cox Plate, adds weight to Boss's argument that the time is right for new stars to emerge.

Nevertheless, it won't be easy for the Danny O'Brien-trained mare who will start her next campaign with earnings just shy of $2 million.

A decade has passed since a four-year-old mare ruled the Melbourne spring when Ethereal completed the Caulfield Cup-Melbourne Cup double.

It's been even longer since one was good enough to win a Cox Plate when the incomparable Sunline won the first of her two weight-for-age championship titles in 1999.

"There's a lot to like about (Shamrocker) but I will say, personally, I've got a question mark on the three-year-olds of last season," Boss said.

"Especially the colts and geldings because (Shamrocker) was able to towel them up and beat them easily."

Shamrocker went close to winning last year's VRC Oaks but she emerged later in the season as a genuine star with her Australian Guineas win and her convincing AJC Australian Derby victory over Retrieve.

Her autumn finished in defeat in the AJC Australian Oaks but she lost few admirers on a heavy track at the end of a long campaign.

Shamrocker is expected to make her spring return under weight-for-age conditions in the $200,000 Memsie Stakes (1400m) at Caulfield on August 27.