At this time of the year, it's hard to find good help for the starting rotation.

If you're one of the unlucky owners to have lost Garrett Richards over the last week (like me, grrrrr), finding a replacement is going to be impossible. There is no one out there who has his ace-level stuff, so you're going to have to make do with a number-four or number-five starter who has gotten off to a solid start.

Luckily, this week's waiver wire leads off with a few arms who have managed to be productive in that role and whose performances going forward give you reason to hope their run of reliability will continue.

Colby Lewis - Texas Rangers (SP)

ESPN Percentage Owned: 20.2%

Colby Lewis' fielding independent pitching (4.86) and strikeouts per nine innings (6.58 K/9) aren't exactly the kind of jaw-dropping numbers that will win you your fantasy leagues. But Lewis has made five straight quality starts for the Rangers and has a 3.12 ERA and a 2-0 record on the season in 52.0 IP.

Lewis is backed by a solid offensive club, so he should be able to pile up some more wins as the season rolls along, and he's in a particularly good groove right now. Over his last four starts, opponents are hitting just .187 against him, and he has pitched six or more innings in all eight starts and at least seven in his last four.

Not bad for a guy who put up a 4.66 ERA in 33 starts last year and a 5.18 ERA in 29 starts in 2014.

Nathan Karns - Seattle Mariners (SP)

ESPN Percentage Owned: 25.3%

Over his last four starts, Nathan Karns has thrown a quality start in all of them, with a 2.46 ERA spanning 25 2/3 innings. He's also become a pretty good strikeout pitcher, averaging 9.44 K/9, with a 3.51 ERA and a 3.88 FIP this season.

Karns is a back-of-the-rotation arm who was acquired via a trade in the offseason from Tampa, with whom he had a 3.67 ERA and struck out 8.88 batters per nine in 147 innings last season. Seattle may limit his innings later in the season, but so far, Karns and his excellent curveball are getting the job done in Seattle.

Matt Wisler - Atlanta Braves (SP)

ESPN Percentage Owned: 12.0%

Atlanta's Matt Wisler may play for a horribly bad baseball team, but his performance this season has been very solid. Over his last three starts, Wisler has a 1.93 ERA in 23 1/3 innings, has allowed just 17 hits, has struck out 13, and has walked just 4.

He's not a big strikeout pitcher, averaging just 5.92 K/9 this season. But opponents are having trouble squaring the ball up against him, as evidenced by his .206 opponents' batting average against, which is tied for 11th-lowest in the National League. Of course, he also has a .224 BABIP, meaning more of the balls that have been getting caught will fall in at some point.

But Wisler has been a solid young starter for Atlanta and should be decent in a pinch for your team if you've lost a stud for a while.

Jonathan Villar - Milwaukee Brewers (SS)

ESPN Percentage Owned: 40.6%

Milwaukee Brewers shortstop Jonathan Villar has been doing this a lot lately.

Coming into Monday, Villar had reached base in 31 of his 35 games this season and has a .391 on-base percentage that is 14th-best in the National League among qualified batters. Overall he's slashing .291/.391/.392 with 16 runs scored, 12 RBI, and 11 stolen bases.

If Villar can continue to get on base like this, he's going to pile up the stolen bases and should be an excellent choice at a position that is very thin in fantasy.

Danny Valencia - Oakland A's (3B/OF)

ESPN Percentage Owned: 20.1%

Danny Valencia had himself quite a day on Sunday.

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Valencia hit 18 homers in 378 plate appearances for Toronto and Oakland last year, and after his three-homer outburst on Sunday, he now has five dingers in 77 plate appearances this season. He's hitting .342/.377/.589 in a platoon role for the A's, and all five of those homers have come in the last three games.

Get him now while he's heating up.

Melvin Upton - San Diego Padres (OF)

ESPN Percentage Owned: 13.9%

I know what you're thinking because I am thinking it too. Why would you want Melvin Upton, who has been one of the worst players in baseball over the last few years, on your fantasy team?

Don't look now, but Upton has been very solid for San Diego this season. In 146 plate appearances, he is batting .281/.363/.453 with 5 homers, 16 runs, and 16 RBI for the Padres. His walk rate is at 11.6%, the highest it's been since 2011 when he was with the Tampa Bay Rays. And his weighted runs created (wRC+) of 123 is his highest since his rookie season way back in 2007.

He's actually played like the player who got a five-year, $75.25 million contract with the Atlanta Braves before the 2013 season and is turning into a potentially valuable trade chip for San Diego later this summer.