Forward Robbie Keane is expected to miss four to six weeks after undergoing knee surgery, the LA Galaxy announced Thursday.

The Galaxy's top scorer the previous four seasons, and assists leader in two of those campaigns, already has two goals in the young 2016 season. But after joining up with the Republic of Ireland but missing the two March friendlies with a knee injury, national team manager Martin O'Neill said Keane wanted to make sure he was fit ahead of this summer's European Championship.

"I think Robbie is just a wee bit concerned about the injury now," O'Neill said last week. "He thought it was a kick for a start, he thought it would clear up in a couple of days. He just felt that it's sore and it's something that he definitely wants looked at, either here [in Ireland] or going back [to America]."

The 35-year-old Keane underwent orthoscopic surgery on his right knee in Los Angeles, according to a Galaxy news release, and will begin working to get back on the field.

The Galaxy have a number of forwards on the roster who they can call upon in his absence. Gyasi Zardes, the American international who coach Bruce Arena deploys in midfield, could slot up top or Arena could deploy turn to forwards like Jose Villarreal, Bradford Jamieson IV, Ariel Lassiter or offseason acquisition Emmanuel Boateng. Veteran target man Alan Gordon also is in the squad.