Prevailing wisdom says a good coach wins and a bad coach loses.

It’s inherently difficult to talk about a coach’s impact without mentioning the won-loss record. It’s their job to win, and their job performance is inescapably tied to that fact.

Winning percentage is the only stat; it remains every coach’s default efficiency rating.

If a coach wins he’s worth keeping around. If not, there’s the door.

And there stands San Jose Earthquakes head coach Mark Watson.

His team wallows in eighth place in the Western Conference as it has for much of 2014, currently mired in an 11-game winless streak that saw San Jose mathematically eliminated from the playoffs last Saturday.

With the club bottoming out at a time when they should be peaking, fans have started calling for Watson’s head, and embracing rumors of Dominic Kinnear leading the club into its new stadium in 2015.

But fans (notably those on Twitter) have been critical of Watson since well before the losing streak, with inconsistent play throughout the season arresting hopes of a bounce back campaign following a disappointing 2013, where Watson’s predecessor Frank Yallop left midseason over “mutual differences” with the front office.

For many, the record is enough to justify the end of the Watson era, but is it fair to blame Watson for a mostly disastrous final campaign at Buck Shaw, or is he merely a scapegoat for a team with issues that run much deeper than who selects the lineup?

* * *

Fresh off a Supporters Shield in 2012, Yallop was out midway through 2013 after a rocky 3-6-6 start. The departure was surprising and the circumstances surrounding it unclear. General manager John Doyle and president Dave Kaval both insisted the long-time manager was not fired (as did Yallop), but many speculated that Yallop left due to disagreements on player personnel.

Whatever the reason, Watson — Yallop’s right hand man — took over for the remainder of 2013. With essentially the same players, Watson led the club to a 11-5-3 record, just missing the playoffs via tiebreaker.

San Jose attempted to improve the roster this offseason, taking creative Portuguese attacker Yannick Djalo on loan, and signing German right-back Andreas Gorlitz to replace departed MLS All-Star Steven Beitashour.

But Gorlitz was out with a season ending injury by May and Djalo was on and off the pitch seemingly every week, with his latest knock coming against Seattle on August 2, suffering a strained right quadriceps. He hasn’t started since.

August 2 was also San Jose’s last victory, and with the injury bug biting both U.S. national defender Clarence Goodson and midseason signing Matias Perez Garcia for much of the season, Watson has had what amounts to a depleted 2013 roster at his disposal.

That’s a roster that even Yallop couldn’t get to produce. The lack of young talented players on San Jose is simply appalling, with not a single player making the MLS’s annual “24 under 24” list. Only 19 year-old Tommy Thompson was nominated.

The Quakes are a very old team in general. Of the 10 players who have appeared most in 2014, seven are 29 or older.

Last year’s team wasn’t very good, doesn’t it make sense that this year’s depleted version is worse? Anybody making the case that this team would have a better record with Yallop at the helm, only needs to look at last season to know that isn’t necessarily the case.

It’s not as if Watson has been stubborn tactically either. When it became clear early in the season opponents had figured out how to thwart San Jose’s direct style, Watson turned to a possession based attack dictated on interplay between the skilled Djalo and Wondolowski up top.

That change in style coincided with a three game unbeaten streak (including the aforementioned victory over first place Seattle) where San Jose outscored their opponents 7-2. Then Djalo got hurt, and the free fall began.

One could argue that this week’s roster predicament — with four players unavailable due to international call ups — is typical of a season where Watson rarely had a full squad to choose from.

It also illustrates that the Quakes are not without international talent, something that could indicate Watson’s inability to get the most out of his players, either motivationally or tactically.

Even with the switch away from the direct approach, Watson’s tactics have always erred on the conservative side.

Watson consistently starts two defensive midfielders — Jean-Baptiste Pierezzi and Sam Cronin — in front of the back four. The idea is that breaking up play in the midfield will stop the opponent from building up an attack, and allows the Quakes to switch to attack without having to play from the back.

Once San Jose falls behind however, they find themselves at a disadvantage, without a midfielder that can run with the ball and create chances.

The club won consecutive games when pairing the attack minded Khari Stephenson and Pierazzi together early in the season. Injuries to Stephenson and others forced lineup changes after the second victory. Two is hardly a large enough sample size to draw a reasonable conclusion, but it remains unclear why Watson hasn’t paired them together since June 1.

The biggest strike against Watson is probably the case of Alan Gordon.

Gordon looked all but done in his nine MLS appearances with the Earthquakes this season, failing to score a single goal. Once a cornerstone of the San Jose attack, Gordon eventually played himself out of the starting lineup, and was even dropped from the 18 by Watson who was coy with the media when pressed for explanation.

Gordon was then traded to Los Angeles on August 11 for allocation money and has gone on to score five goals in seven appearances as a center forward for Bruce Arena and the second-place Galaxy.

For whatever reason Gordon’s form clearly spiked when he headed south. It could be as simple as a change of scenery, but anytime a player moves and immediately improves it does not reflect well on the previous coach.

* * *

The Earthquakes did pretty well under Watson in 2013, nearly making the playoffs despite a disastrous start.

So what changed?

Maybe Watson’s a bad coach and last season’s surge was a fluke. Maybe he’s a good coach in charge of a weak roster with consistent injury and age issues. Maybe both are true, and possibly neither.

If you want to blame Watson for a forgettable 2014, go ahead. He might deserve it. Just like Doyle might, Kaval might or the players might. All are likely playing their part.

Watson is the coach of a losing team, without a track record to lean on. That puts him first on the chopping block for better or worse. Only time will tell which one it is.

Follow @SFBay and @jakemmontero on Twitter and at SFBay.ca for full coverage of the San Jose Earthquakes.