As the 49ers enter the rebuilding month of April and the upcoming draft, here are some holes the franchise should address:

-- Find a pass rusher to add punch and depth, ideally through the draft. Now that the defense has settled on a 3-4 scheme, is Kentwan Balmer a game-changing pass rusher? Can linebacker Manny Lawson be that man?

-- Find a No. 1 receiver. Isaac Bruce has been given an April 1 deadline to tell the team whether he intends to return. His silence indicates he is not returning. Second-year receiver Josh Morgan, the team's best draft pick in 2008, says he is prepared to assume the go-to role. But he is raw, inexperienced and still dependent on Bruce's mentoring. Meanwhile, solid free-agent receivers - Nate Washington, Jabar Gaffney, David Patten - are now off the board.

Why not sign Amani Toomer and tell Bruce to call it a career?

-- Draft a right tackle with the No. 10 overall pick. Free-agent Marvel Smith might provide depth, but this is an important position that should be addressed with a long-term solution. Mississippi's Michael Oher has the talent and character to fit in Singletary's system.

Singletary's inaugural minicamp, an early offseason bonus for him as a new NFL head coach, figured to give him and general manager Scot McCloughan an advantage - a clear snapshot of what the 49ers might need entering the free-agency "value period," when less flashy (and expensive) starting candidates, valuable backups and quality special-teams contributors can be signed to bolster depth at key positions. It also will help them plan for the April 25-26 draft.

The camp, conducted several weeks before other teams are even considering mandatory workouts, had good participation and lots of team-building exercises, along with circuit and conditioning drills.

Players ran with heavy bags in relay races. They stared in awe at the 15-foot conditioning hill Singletary added to the north end of the practice field. The weekend looked more like an organized team workout than a typical minicamp with specific position drills.

Singletary made it clear all of this was designed to "set the tone for the season."

Consider who was missing in Santa Clara:

-- Bruce. The wide receiver was given the April 1 deadline as part of Singletary's straight talk.

"Isaac, obviously he's played a long time and I'm sure in his mind he has every right to say, 'I'll let you know when I get ready,' " Singletary said of his 36-year-old receiver. "But at the same time, we have a football team and if you're a part of that team, then you've got to let us know at a certain time. And he will. I have no doubt about that."

-- Offensive tackle Jonas Jennings, who essentially has been told he's not in the 49ers' plans. That means there is no solution at right tackle for an offensive line that surrendered an NFL-high 55 sacks in 2008, unless the 49ers believe Barry Sims and Adam Snyder are the answer.

Sure, the 49ers made an offer to Smith, the Steelers' free agent. But if Smith - a player with a history of back problems and not a lot of suitors - was enamored with being on board, they probably would have signed him by now.

-- An experienced quarterback to complement (or compete with) Shaun Hill and Alex Smith.

The quarterback issue is a given, and it's also a contradiction.

Consider this conversation with McCloughan during the NFL scouting combine in Indianapolis last month, when I specifically asked him whether he would consider signing a veteran quarterback during the looming free-agency signing period.

McCloughan made it pretty clear the 49ers wouldn't pursue any of the top-dollar quarterbacks, hoping to focus instead on building depth at the position through value free agents or the draft.

Then the 49ers willingly became pawns in Kurt Warner's leverage game to extract more money from a team he didn't intend to leave, the Cardinals.

Straight talk is what you get from Singletary. Straight answers ... not so much.

Three times, Singletary was asked whether the first minicamp was providing any insight as to what he might seek in the draft. Twice he answered by emphasizing the bonding and character-building taking place during on-field drills.

Finally, he said he wasn't bothered by what was missing on the field.

"Oh, there's no doubt about it. I think the core of what we need is right here," Singletary said.

Then again, maybe not.

E-mail Nancy Gay at ngay@sfchronicle.com.

This article appeared on page D - 1 of the San Francisco Chronicle