It's expected to be two steps forward and one step back for the Waratahs this weekend, with the return of Justin Harrison and Mat Rogers set to offset the likely loss of giant flanker Wycliff Palu for the Super 12 match against the Hurricanes.

While Daniel Vickerman did not train on Monday, concerns eased over the shoulder injury he sustained against the Crusaders.

The former South African was found to only have bruising and he is likely to reform his effective second row combination with Harrison who comes back after serving a three-week suspension for racially abusing Cats winger Chumani Booi.

Palu is in extreme doubt however, the 120kg wrecking ball sustaining nerve damage in his shoulder.

"With those kind of injuries you just don't know - he could come good tomorrow or it could take a little bit longer," Waratahs coach Ewen McKenzie said.

"I'm not as confident with Cliffy having been a victim of nerve related injuries myself they are very unpredictable.

"It's just a waiting game there it's not as if you can speed it up."

Captain Chris Whitaker, openside flanker Phil Waugh and reserve forward Alex Kanaar had spells during the session on Monday but should all be fit for the top of the table clash.

McKenzie said Harrison would be a substantial addition to the side.

"I sense that he's feeling pretty keen about getting back involved and giving us something. He is certainly a key player for us.

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