Chemistry is an elusive, unpredictable connection between the quarterback and his receivers in any offense. It can’t be quantified, and therefore we’re never totally sure of its existence. At times it’s just another easy cliché for the hack color commentator, and much like a quarterback with poise or a running back who sees the field, having or not having chemistry is the standard umbrella classification for a QB/WR duo.

So I apologize for resorting to such hackery, but chemistry is also a term used by writers confused by Chad Ochocinco and his disappearance in New England. Sure, I could blame age, but it doesn’t feel like Ocho’s plight can be pushed aside that easily. It’s a little more deep-rooted.

Ochocinco is 33 years old, and long before Bill Belichick took a chance on another malcontent player in late July his decline was clear, although slightly exaggerated. His career-high in receiving yards came back in 2007 when he finished with 1,440, good enough for third in the league. His body then began to wear down over the next three seasons and he missed five games. But in 2009 and 2010 he still had a combined 139 receptions, 1,878 receiving yards, and 13 touchdowns, which are respectable numbers for a player on the wrong side of 30.

Like running backs, wide receivers can often experience a sudden drop-off in their early 30s, a cliff dive most recently executed by Terrell Owens and Randy Moss. But the incline of Ocho’s cliff is particularly steep since he’s on pace for only 18 catches and 272 yards this year, both easily career lows. In his rookie year when he played sparingly and appeared in only 12 games–starting three–Ochocinco had 28 receptions and 329 yards.

It gets worse, and Chad Finn of the Boston Globe shared some of Ochocinco’s scary numbers:

He was held without a catch yesterday despite being the intended receiver for more of Brady’s passes than he has during any of the previous seven games this season.

Entering the game, Ochocinco had been targeted 16 times, with nine receptions for 136 yards.

Last year with the Bengals, he was targeted at least five times in 13 of 14 games. During the 2010 season opener against the Patriots, he was targeted 13 times — and caught 12, for 159 yards.

Yes, it’s true. His numbers in one game against the Patriots last year surpass what he’s accomplished in eight games with the Patriots this year.

Between 2003 and 2010, Ochocinco experienced the embarrassment of being held without a catch just once. Now he’s posted a circular figure in three straight games.

All of this paints Ochocinco as a veteran receiver whose athleticism is rapidly declining, and who no longer possesses the agility to run effective routes, the same routes designed to create open space for receptions.

But again, there’s something deeper than age here, and there are signs that Ocho’s inability to mentally grasp the New England offense may equal his physical deficiencies. Ochocinco and his quarterback Tom Brady were animated on the sideline after one misfire in the second half of yesterday’s loss to the Giants, and Ocho later held up two fingers when speaking to the Boston Herald, saying they’re missing by “this much.”

In his regular Monday interview with WEEI in Boston, Brady said that working Ochocinco into the Patriots’ offense remains an ongoing weekly effort.

“Every week there’s more confidence in what we’re doing with him, and with him and me. It’s just a matter of us getting out there and doing it on the field. Believe me, no one’s more frustrated than us. We talked after the game about what we need to do to get better. And we’re just going to keep doing it. We really don’t know any other way.”

Ochocinco is a 10-year veteran, and he’s had 97 days to learn and grow as a productive piece of New England’s offense. Yet he still has fewer receiving yards than renowned household names like Scott Chandler, Dennis Pitta, and Randall Cobb.

If Ochocinco still needs precious one-on-one time with Brady to grasp core offensive concepts, it’s difficult to understand why he’s still occupying a roster spot in an offense that already has a veteran receiver (Deion Branch), and a passing game that runs primarily through Wes Welker and the two young tight ends.

Sheer stubbornness is likely holding Belichick back since Ochocinco will make $6 million this year and he cost the Pats two draft picks, and maybe more consideration would be given to Ochocinco’s dim future if Taylor Price and Julian Edelman could stay healthy. As it stands, Ochocinco will likely be in a Patriots uniform for at least the rest of this season.

After that he’ll be another veteran Belichick castaway just like Moss and Leigh Bodden, or at least he should be.