Barring an unforeseen blockbuster trade, the time to add an ace this offseason has come and gone. But that doesn't mean there aren't rotation upgrades available.
There may not be a sure thing remaining on the pitching market, but quite a few second- and third-tier arms could slot nicely into a playoff-bound rotation. (After all, one year ago, Chris Young and Edinson Volquez were lower-level free agents. Now they're World Series champions.)
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That's not to say there isn't risk in signing one of the remaining free agents. There's plenty of it, in fact. Here's a look at those pitchers, and the pros and cons for signing each.
Wei-Yin Chen
Upside: Chen is the most reliable of the remaining starters, and he comes with the fewest question marks. He's made more than 30 starts in three of his four seasons and typically sits around the 190-inning mark. Chen is by no means an ace, but slot him in the middle of the rotation and you've got a reliable pitcher who can take the ball every fifth day and win more often than not.
Downside: Chen's consistency means he'll come with a significant price tag -- probably the highest of the remaining pitchers. His original four-year, $15.75 million deal with Baltimore was undoubtedly a steal, but his next contract almost certainly won't be. That especially holds true if Chen is looking for a five-year deal -- at the end of which he'd be 35.

Yovani Gallardo
Upside: Still just 29, Gallardo is relatively young for a free-agent starter, and if you're a believer in ERA as a tell-all, he might be your guy. Gallardo posted a 3.42 mark while pitching in one of the tougher pitcher's parks in Texas. That was good enough for a 124 ERA+. Plus, Gallardo has made at least 30 starts in each of his past seven seasons.
Downside: Unfortunately for Gallardo, prospective suitors will be looking at more than just ERA, and he simply didn't miss enough bats in 2015. Gallardo's strikeout rate hovered around 25 percent with the Brewers from 2009-12. It went down to 15.3 percent last season. His 6.5 swinging-strike percentage was easily the lowest of his career, and his 1.42 WHIP is surprisingly high for a pitcher with an ERA so low, which could indicate future regression.

Ian Kennedy
Upside: It wasn't so long ago when Kennedy won 36 games over a two-year stretch with Arizona. Unlike Gallardo, his strikeout rate of 9.3 in 2015 was a career high -- and he walked fewer hitters, too. Kennedy's average fastball velocity last season was 91.3 mph, higher than his career average. Yes, Kennedy is prone to having a few outings in which he gets hit hard. But he clearly has the stuff to dazzle every once in a while as well.
Downside: When Kennedy isn't striking out hitters, he gets hit -- hard. Kennedy's rate of hard contact against last season was 35.2 percent, easily the worst in the Majors, according to Fangraphs. He also tends to give up a lot of fly balls, which -- as you'd expect -- doesn't mix well with the hard contact. Kennedy's 1.66 homers per nine last season was the highest rate in the Majors. In addition, Kennedy turned down a qualifying offer from San Diego, meaning the team that signs him would forfeit a Draft pick.

Doug Fister
Upside: Fister seemed like an obvious top-five free-agent starter a year ago. Now he might be the biggest enigma of the bunch. For the purposes of his upside, let's focus only on the pitcher Fister was before his forearm trouble last year. He recorded ground balls at a rate of about 50 percent and was rarely vicitimized by walks or home runs. Plus, Fister is just one year removed from a 2.41 ERA and a 1.08 WHIP in 2014.
Downside: Fister's fastball velocity is the biggest concern for prospective suitors. His average dropped from a career mark of 88.4 to 86.2 mph in 2015 -- likely the result of a flexor strain in May. The impact was clear as day. Fister's ground-ball rate of 44.6 percent was a career low, and his hard-contact rate of 29.5 percent was a career high. He was relegated to the Nationals' bullpen by mid-August. If Fister can regain his old form, he's a free-agent steal. But for a 32-year-old coming off arm troubles, that's a major "if."

Mat Latos
Upside: It's not every day that you'll find an affordable 28-year-old starter on the market with three 14-win seasons under his belt. Latos' age and price tag are pluses for whichever team signs him. Last season was ugly, as he posted a 4.95 ERA with three clubs. But Latos went 33-16 with a 3.31 ERA in his three prior seasons with Cincinnati. There's clearly some talent in Latos' right arm, and despite the struggles, he did not see a velocity dip in 2015.
Downside: There's a reason a pitcher with such a solid resume at such a young age would be so relatively cheap. Latos' ERA+ of 78 sandwiches him right between Kyle Kendrick and Alfredo Simon among pitchers who threw at least 100 innings in 2015. The former signed a Minor League deal this offseason, and the latter might not get a guaranteed big league contract, either. Latos is probably not a candidate for anything more than a one-year deal -- which could be just what he needs to prove himself worthy of a larger contract next offseason.

Tim Lincecum
Upside: Given all his ups and downs, it's hard to believe Lincecum is only 31. The two-time National League Cy Young Award winner hasn't posted a sub-4.00 ERA since 2011, but he's had a few moments -- including a brilliant showing (mainly as a reliever) in the '12 postseason and a pair of no-hitters. No one on the market has the experience of Lincecum, and he'll be a cheap option to put at the back end of a rotation.
Downside: Not only are Lincecum's recent numbers down, he's also coming off a season riddled with hip injuries. Lincecum's struggles are largely the result of his declining fastball velocity -- his four-seamer, which averaged 93.2 mph during his NL Cy Young Award-winning seasons of 2008-09, was down to 87.5 mph in '15. And that steep decline has precipitated an overreliance on the changeup -- once his most dominant pitch but now entirely lacking in deception. It's difficult to imagine a '16 version of Lincecum that resembles anything close to the Lincecum of old.