SAN FRANCISCO — This was supposed to be the week that Michael Crabtree showed the Oakland Raiders they made a colossal mistake in drafting Darrius Heyward-Bey instead of him with the seventh pick in April’s draft.

Crabtree, widely considered the best receiving prospect going in the draft, dropped to the San Francisco 49ers at 10th overall after Oakland surprised the pundits by selecting the speedy Heyward-Bey.

With the 49ers spending two days at the Raiders practice facility in Napa for a joint practice before tonight’s exhibition game between the two Bay Area rivals, the Raiders were expected to get a firsthand look at Crabtree.

Yet the receiver won’t be at Candlestick Park for the annual meeting as he remains a contract holdout, reportedly looking for a deal worth at least as much as the $23.5 million guaranteed that Heyward-Bey got despite being taken three spots later.

With Crabtree holding out, that will take some pressure off Heyward-Bey, who was the target of harsh criticism on draft day.

“I’ve always been concerned with myself and only me from Day 1,” Heyward-Bey said. “I really can’t worry about what everybody else is doing.”

Heyward-Bey has struggled holding onto passes in practice in his rookie training camp. He also was unable to get open on his two deep attempts in Oakland’s exhibition opener against Dallas last week.

Heyward-Bey caught one 8-yard pass in his half of action against the Cowboys. But with Chaz Schilens out four to six weeks with a broken bone in his left foot and Javon Walker still not back from offseason knee surgery, the Raiders are counting even more on Heyward-Bey.

Quarterback JaMarcus Russell sees progress from his rookie receiver but also said he needs to work on proper releases from the line of scrimmage and other technical facets of the game in order to be able to capitalize on his blazing speed.

“It’s just one of those things where he’s got to get it second nature in his mind so on certain plays, ’I must do this, I must do that,”’ Russell said. “But if I can help him by throwing the ball out of bounds and talk to him back in the huddle or the next play, then we’re going to do that. At the same time, those guys will see his speed and those safeties were getting over pretty fast.”

Raiders owner Al Davis is infatuated with speed and was attracted to Heyward-Bey after he ran the fastest 40-yard dash time of any player at the NFL combine at 4.3 seconds.

That speed caught the attention of the Cowboys in the exhibition opener, with Dallas providing safety help anytime Heyward-Bey tried to go deep. The 49ers also got an up-close look at it during the joint practices Tuesday and Wednesday.

“He’s fast, a world-class sprinter,” Niners cornerback Dre’ Bly said. “He seems likes he’s a hard worker. He needs to work on his hands a little bit, but that will come if he works hard. You have to careful with him on the deep route.”

Crabtree is one of only two first-round picks without a contract, joining sixth pick Andre Smith of Cincinnati. As each day goes by with Crabtree unable to practice and learn an NFL offense, it becomes less and less likely that he will be able to make a significant contribution this season.

Crabtree will have to play catch-up when he finally does arrive, with the task growing tougher and tougher with each day of practice he misses.

“I’m not thinking about it a whole lot,” coach Mike Singletary said. “These receivers who are here, they are busting their tails day in and day out. Those are the guys we are evaluating. ... We are just going to continue to move forward. I’m still excited about Crabtree and the athlete he is, and at some point in time, what he brings to our team.”

With no comparison between the top two receivers in the draft being possible Saturday night, the biggest question will be the competition between San Francisco’s two quarterbacks.

Alex Smith will get the start tonight after Shaun Hill started the exhibition opener. The two are each expected to get about 15 snaps in the game as Singletary tries to determine who will be the starter when the season starts.

“I’m starting to see some of the things we need to see,” Singletary said. “It is not like one is running away with it or anything like that, it is just one of those things where you get to a point and you have to make a decision and go with your gut.”

Smith lost a preseason competition with J.T. O’Sullivan last year and ended up missing the entire season after undergoing shoulder surgery.

He knows this game could be his last chance to show that he should be the starter and is capable of being the player the Niners hoped they got when they picked him first overall in 2005.

“It’s obviously something that’s on my mind,” Smith said of the competition. “We go out there every day and we split the reps. That’s going to change here one of these days. ... I don’t obsess about it. I think about it, but I’m really trying to focus on what I have to do or what I can control.”