SAN JOSE, Calif. -- A camera crew has been shadowing the San Jose Earthquakes this week, capturing images for future TV commercials. By the time those ads are cut, however, several of the faces in the background likely will have disappeared from the Quakes’ roster.

With 39 bodies on the training pitch Thursday, San Jose is still sorting through numerous options for possible use in defense of their 2012 Supporters’ Shield. The picture should be coming much more into focus after the club travels to Portland for an eight-day, three-match trip that will leave the club just eight days out from its season opener against Real Salt Lake.

“Don’t ask everyone’s names. I don’t know them,” Quakes coach Frank Yallop half-joked to reporters, before turning more serious: “After the next three days, there’ll be a few guys not here.”

San Jose has currently filled 26 of their 30 roster spots, including defenders Nana Attakora and rookie Peter McGlynn, whose deals are expected to be announced soon. (The cat may be out of the bag regarding McGlynn, who tweeted Tuesday, “Just signed first professional contract!!”) With another slot presumably reserved for first-round draft pick Tommy Muller, space is at a premium -- which would seem to dampen the need for a plethora of trialists.

Nevertheless, the Quakes have made sure to cover all their bases with so many of their regulars nursing injuries. Mehdi Ballouchy, Alan Gordon and now Steven Beitashour -- who underwent surgery Wednesday -- are expected to miss the start of the season. Marvin Chavez, Steven Lenhart and Marcus Tracy have trained sparingly, while Muller, second-round pick Dan Delgado and stalwart center back Jason Hernandez are being monitored carefully as they battle nagging problems.

“All the guys we’ve brought in are serious looks for us,” Yallop said. “It’s not like we’re bringing guys in for numbers. We like all the fellas that we’ve brought in. We think at least they can compete with our group and try to get a place. There’s not many spaces, but we want to give everyone a chance to train and do their thing.”

The biggest long-term issue is how to replace the offensive punch of Simon Dawkins, whom the Quakes lost when he was sent by Tottenham Hotspur on loan to Aston Villa. San Jose had been trying to win Dawkins’ services full-time from Spurs after seeing the young Englishman score 14 goals on loan in 2011-12

Among the more intriguing names to potentially fill in for Dawkins are John Bostock and Cordell Cato.

Bostock is another Tottenham product who could stay on a loan until his Spurs deal ends in June. Yallop said the team is not yet looking at anything longer term with Bostock, who could play throughout midfield or as a second forward.

The speedy Cato trained for several weeks with the Quakes late in the lost 2011 season. He spent last year with Seattle, scoring the only goal in the Sounders’ 1-0 win against San Jose in a contentious US Open Cup quarterfinal.

Another player who appears to be on the bubble for a roster berth is Sierra Leonean midfielder Abu Tommy, who has outlasted several competitors to get to this point.

“He’s done well,” Yallop said. “The next week or so will really determine if we’re going to sign him or not. He’s stayed around long enough, and you know me, if they’re not good, they’re gone in a few days.”

Geoff Lepper covers the Earthquakes for MLSsoccer.com. He can be reached at sanjosequakes@gmail.com. On Twitter: @quakesbeat