(Reuters) - Arsenal defender Per Mertesacker rued his side's "massive loss" to West Ham United on Sunday but was confident the Gunners will bounce back from the setback in their Premier League opener. The Germany international bemoaned his side's lack of decisiveness in front of goal as Arsenal were well beaten by a West Ham side that defended strongly and looked to hit their London rivals on the break. "It's a massive loss for us," Mertesacker was quoted as saying on the club's website (www.arsenal.com). "Overall, we weren't decisive enough, especially in the final third. ... Click here to read full news..