Just as quickly as Mark Clayton developed into the Rams' go-to receiver, the team must now find other options to replace the 5½ catches and 75 yards that he averaged in his first four games.

Clayton is out for the season after suffering a torn patellar tendon in his right knee in the first quarter of Sunday's 44-6 loss to Detroit. Over the short term, the Rams must find more production from within the roster.

The promotion of former University of Missouri wide receiver Danario Alexander to the active roster from the practice squad, which should become official today, may pay big dividends in the long run. But over the short term, Alexander may not have much of an impact as he continues to work his way back to health from left knee surgery last February.

Trades such as the one that brought a quality player (Clayton) to St. Louis for next to nothing don't happen very often in the NFL. And it's unrealistic to think that lightning could strike twice.

"Trades and all those things, it's great for fantasy football, but it doesn't always work," coach Steve Spagnuolo said. "So you're always trying to develop the players that are in the program here, and Nolan (Cromwell) has been doing that with all these guys."

Cromwell, the Rams' wide receivers coach, is earning his money this year. Clayton is the third Rams wideout to go on injured reserve this season, joining Donnie Avery and undrafted rookie Dominique Curry — both of whom also suffered season-ending knee injuries.

Quarterback Sam Bradford quickly developed a chemistry with Clayton and Danny Amendola. Now that Clayton is out of the mix, some combination of Brandon Gibson, Mardy Gilyard and Laurent Robinson must step to the forefront.

"Mardy Gilyard has been getting more reps every game," Spagnuolo said. "He's been getting more touches, and he's been getting better. Brandon Gibson's getting better. Laurent Robinson is just coming off an injury (foot), so he's kind of fighting that.

"We certainly don't feel good about losing Mark because he made a lot of plays for us, but we're going to find a way to overcome that somehow."

Help in the passing game could also be on the way this week from the tight end position. Michael Hoomanawanui and Billy Bajema both said Monday they would be full-go in practice this week and barring any setbacks planned to play this Sunday against San Diego.

Bradford threw a lot to the tight ends during the preseason, and it looked like that would be an added wrinkle to the offense this season. But Hoomanawanui — who led the Rams in preseason catches (nine) and reception yards (139), and shared the team lead in touchdown catches (two) — suffered a high left ankle sprain early in the season opener against Arizona. The following week in Oakland, Billy Bajema suffered an MCL injury to his right knee.

That left Bradford with only one true pass-catching option at tight end in Daniel Fells. (Rookie Fendi Onobun, after playing just one season of college football, is still finding his way in the NFL.)

The original timetable for Hoomanawanui was a return before the Rams' bye week the first week of November. If he indeed ends up playing against San Diego, he'll be a couple of weeks ahead of schedule.

"The trainers have done a good job of getting me back a little earlier than expected," Hoomanawanui said Monday. "I'm a quick healer. So I'm excited to be out there this weekend."

Can he pick up where he left off in terms of chemistry with Bradford?

"That's the plan," he said. "With Mark going down, everyone has to step up. Not just me; not just the tight ends. So the receivers, tight ends, running backs, everyone's going to have to step up."

Meanwhile, Bajema was encouraged about his availability for San Diego after a running session Monday.

"I'm close," he said. "I should be out at practice on Wednesday. And if all goes well, I'm looking forward to getting back on the field (against the Chargers)."

Back at wide receiver, Gilyard is the most likely immediate replacement for Clayton in the starting lineup because he's most familiar with the position Clayton played — flanker. Gilyard said he has reached the point where he's fairly comfortable in the offense.

"All in all, I've pretty much grasped the concept of the offense," Gilyard said. "I don't have it all the way down — I'd be lying if I said I had it all the way down to the 'T.' Because it's a lot of stuff."

Gibson, who moved into the starting lineup at split end when Robinson was sidelined with a foot injury following the Oakland game, is still knocking off some rust after missing much of the spring practices as well as training camp with hamstring issues.

"My biggest thing is just getting out there and trying to work through the tough spots," Gibson said. "The dropped passes, and not separating (from defenders). That kind of stuff."

As for Alexander, atrophy in the leg muscles following surgery had the Rams concerned about bringing him along too quickly. But Alexander has worked hard to build up his leg and apparently is close enough to full strength to merit a promotion to the 53-man roster.

"He's excited about doing it," Spagnuolo said. "But the health of the player, to me, is important."