Excuse me. Do you mind if I throw a stink bomb into the confetti?

I assume the reports are true. I assume that the 49ers have indeed traded quarterback Alex Smith to the Kansas City Chiefs for a sweet brace of draft picks. I assume it will be announced March 12, the first official day such deals can be consummated.

I assume that Smith is cool with this transaction, because he can now be a starter rather than sitting behind Colin Kaepernick, as happened in the final 10 games of 2012. I assume that the 49ers are giddy to now possess a potential 15 picks in this year's draft, including two of the first 34 selections. I assume most of the team's followers are in happy-happy-joy-joy mode about all of it.

Fair enough. I will remember this cool and giddy and happy-joy day in October, when a theoretical Sunday might produce a theoretically injured Kaepernick and put the 49ers in a theoretical very not cool or giddy or happy-joy situation.

Kaepernick was close to wondrous when he became the 49ers starter. His legs and arm were indeed visibly superior to Smith's, validating the gutsy choice by coach Jim Harbaugh. But those legs, in particular, make the Kaepernick decision a double-edged sword. But his ability to run the ball makes him a huge threat and a vulnerable target.

That's what the Washington Redskins learned when double-edged sword quarterback Robert Griffin III messed up his knee early in their playoff game and played ineffectively before his offseason surgery that leaves his 2013 status in doubt. That's what the Philadelphia Eagles learned when double-edged sword quarterback Michael Vick missed three weeks of the 2012 schedule because of injury.

Neither the Redskins nor the Eagles had a backup quarterback as good as Smith waiting to run onto the field and save them. And now, neither do the 49ers.

Oh, it might work out just swell. I know that.

If Kaepernick is great and healthy for all 16 games plus playoffs in 2013 . . . then no worries.

Or if Kaepernick is hurt and the 49ers receive a bang-up performance from quarterback Scott Tolzien, who has been on the 49ers' roster for two-plus seasons and has shown promise . . . then no worries.

Or if the 49ers acquire a veteran backup before training camp or utilize their newly acquired second-round draft pick to select a college quarterback with Kaepernick-like qualities to develop (I'm thinking about Florida State's E.J. Manuel or Arizona's Matt Scott) . . . then no worries.

But if Tolzien isn't ready and no veteran is acquired and no skilled rookie quarterback is drafted, then . . . uh, worries. Potentially big worries.

Even if Kaepernick's legs remain unharmed, we don't know what will happen when NFL defensive coordinators have time to examine his game and his tendencies more closely during the offseason. He seems like the real deal. But there are no guarantees. The Baltimore Ravens managed to confuse Kaepernick at times in the Super Bowl. Other coaches are studying that video. Are 10 games enough to proclaim that he can be an NFL starter forever?

I could be respecting Smith too much. During his tortured and difficult eight years with the 49ers, he had basically one and a half good seasons. But he has stayed classy throughout. And as a South Bay resident, was particularly active in local community work that often went unpublicized. He deserves nothing but good fortune with his new team.

And yet . . . well, in the wake of Wednesday's trade news, there were the inevitable references to the most storied quarterback trade between the 49ers and Chiefs -- the 1993 deal that sent Joe Montana to Kansas City. That transaction opened the door for Steve Young to become the uncontested 49ers starter, and he won the Super Bowl a season later. Thus, history records the trade as a glorious success in the Bay Area.

However, there were moments during the 1993 and 1994 seasons when that history appeared on the verge of being written differently. In 1993, Montana won two playoff games for the Chiefs. Young racked up a single postseason victory with the 49ers -- and both teams lost in conference title games. Early in the 1994 season, Montana beat the 49ers in a head-to-head matchup. All of that was superseded by Young's championship run.

Also, the law of unintended NFL consequences could well come back to bite the 49ers. With Smith joining the Chiefs, it means Matt Cassel will surely leave Kansas City. He could therefore wind up with the Arizona Cardinals, who are also seeking a starting quarterback. The 49ers were wisely not going to trade Smith within their division. But if Cassel, who won a division title with the Chiefs in 2010, should end up in Arizona and help boost the Cardinals back into contending status -- or deal a costly defeat to the 49ers -- don't forget how he got there.

Conventional wisdom is that the 49ers could not have kept Smith for financial reasons, because they owed him more than $8 million for the 2013 season. A trade undeniably beats releasing him with no return compensation. But the truth is, the 49ers could have afforded Smith because Kaepernick will make less than a million bucks in 2013.

True, there will still be salary relief, allowing the 49ers to spend extra cash on other players and other positions. Yet no position is more important than quarterback. And if, heaven forbid, Kaepernick limps off the field in Week 5 with a season-ending injury, will that extra cash be running onto the field to replace him? Or will it be a human being who isn't as experienced or capable as Smith?

Ponder the answer to that question as you sweep up the celebration confetti after this trade. I'm not saying. I'm just saying.

Contact Mark Purdy at mpurdy@mercurynews.com. Follow him on Twitter at twitter.com/MercPurdy.

Inside
Alex Smith reportedly is dealt to the Chiefs for two draft picks. page 2.

ONline extras
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K.C.-S.F-QB connection
Alex Smith becomes the fourth quarterback since 1993 to go directly from the 49ers to the Kansas City Chiefs.
  • 1993: Joe Montana, S David Whitmore and 1994 third-round pick traded to Kansas City for Chiefs' first-round pick in 1993. 49ers traded that pick to Arizona (then Phoenix) Cardinals.
  • 1994: Steve Bono traded to Kansas City for Chiefs' fourth-round pick in 1995.
  • 1997: Elvis Grbac left 49ers to sign as free agent with Kansas City.
  • 2013: Alex Smith traded to Kansas City for second-round pick in 2013 draft and conditional pick (second or third round) in 2014 draft.
  • Quarterback Steve DeBerg, who began his career with the 49ers in 1977, eventually became a member of the Chiefs in 1988, with stops in Denver and Tampa Bay in-between.