The Stamford Bridge surface was treacherous as the game was played in a torrential downpour .
The conditions encouraged Lampard to test Helton with a low shot from 20 yards that the Porto keeper dealt with in less than convincing fashion .
The Stamford Bridge surface was treacherous as the game was played in a torrential downpour , and the conditions encouraged Lampard to test Helton with a low shot from 20 yards that the Porto keeper dealt with in less than convincing fashion .