St Kilda coach Ross Lyon has conceded it's time to rethink his team's tall forwards strategy in the wake of Saturday's 42-point loss to Geelong at Telstra Dome.

The Saints' three big guns, Nick Riewoldt, Justin Koschitzke and Fraser Gehrig managed to score eight of their team's 13 goals between them against the Cats, but Lyon was more concerned about the lack of team defence inside the forward 50.

Gehrig's effort was telling as he was banished to the forward pocket at times in a vain attempt to take Matthew Scarlett out of the play.

But the Geelong full-back was still able to gather 24 possessions and six marks by running off his opponent.

"I think clearly, (the three talls system) is under pressure, it's under pressure," Lyon told his post-match media conference.

"We've got to improve our forward 50 pressure, everyone knows that … and we'll look at that."

"The last two weeks the opposition has scored too easily so our team defence from the front 50 to the midfield to the back end needs to improve, and quickly."

Otherwise, Lyon was upbeat about the Saints' performance, noting that their two defeats so far this season had been at the hands of unbeaten teams sitting atop the ladder.

"Not taking our opportunities early put some scoreboard pressure on and then in the second quarter they really got to work … there was a significant swing from quarter to quarter and that's what we're trying to understand because the plans don't change but the results did," Lyon said.

"I'm not sure of the scoreboard exactly indicates it but at no stage did our group give up."

"There were some horrible skill errors but … our centre square group of Hayes, Montagna, Ball and Dal Santo were desperate right to the end."

"I thought for three quarters we competed pretty well but they’re a class team and every error we made they capitalised on."

"It's certainly not doom and gloom."

Lyon said he had no choice but to ask Robert Harvey to return to the field in the second half after the veteran midfielder suffered a corked thigh in the second quarter, and it was a similar scenario for Xavier Clarke who was concussed by a heavy bump from Geelong ruckman Trent West, also in the second quarter.

"Unfortunately, you need to put players on," Lyon said.

"(Harvey) was limited but he could take the field so we needed to share the load."

"At the end of the day it was a cork - he wasn't zinging around but he could move."