[4][5][6] Welker played college football for the Texas Tech Red Raiders, where he won the Mosi Tatupu Award and was a first-team All-Big 12 as a senior.

Joining the NFL in 2004, Welker played his first three seasons with the Dolphins and set the franchise record for kickoff return yardage.

Based on a highlight reel from high school, Welker earned the nickname "The Natural", given to him by his recruiter, and then running backs coach at Texas Tech, Art Briles, before his freshman year for his versatility and big-game performances.

He had four total punt returns on the day for 102 net yards for a 25.5 average[18] On October 7, against Baylor, he recorded his first collegiate reception on a 37-yard catch in the 28–0 victory.

[35][36] In the first three games of the 2003 season, Welker totaled 16 receptions for 183 yards and recorded a punt return touchdown in a 58–10 victory over SMU in that stretch.

[44][45] In 2003, Welker won the Mosi Tatupu Award, given annually to the best special teams player in college football.

[52] Head coach Marty Schottenheimer later acknowledged that in terms of roster cuts, releasing Welker was the "biggest mistake [he] ever made".

Although the Chargers offered him a slot on their practice squad, Welker chose to sign with the Miami Dolphins, where he was mostly used on special teams.

[54] Playing against the New England Patriots on October 10, 2004, Welker became the second player in NFL history to return a kickoff and a punt, kick an extra point and a field goal, and make a tackle in a single game.

[60] During training camp at the beginning of the 2005 season, Welker was promoted to the third wide receiver spot after Chris Chambers and Marty Booker.

[64] On October 8, 2006, he was a reliable target for back-up quarterback Joey Harrington, recording a then career-high nine catches for 77 yards in a 20–10 loss to the New England Patriots.

[66][67] On March 1, 2007, the Dolphins offered Welker, a restricted free agent, a second-round tender of $1.35 million for a one-year contract.

According to The Boston Globe, that sheet would have contained a poison pill provision that would have made the offer difficult for the Dolphins to match.

[75][76] In Week 17, in a game against the New York Giants, he caught 11 more passes, setting the Patriots franchise record for catches with 112, and tying Bengals receiver T. J. Houshmandzadeh for most receptions in the 2007 NFL season.

[79][80] In his first two postseason games, the Divisional Round against the Jacksonville Jaguars and the AFC Championship against the San Diego Chargers, Welker had 16 receptions for 110 yards and two touchdowns.

[87] Welker had what was, at the time, the longest pass play of his NFL career in the Patriots' 48–28 victory over the Miami Dolphins in Week 12: on 2nd-and-8 from their own 15, Welker caught a five-yard pass from Matt Cassel, then eluded a pair of defenders, tip-toeing and running down the left sideline to the Miami 21, for a total of 64 yards, 59 yards after the catch.

[96] He was sidelined in Weeks 2 and 3, against the New York Jets and Atlanta Falcons, respectively, with a knee injury; rookie wide receiver Julian Edelman took his place in the lineup.

[97][98] In the Week 6 game against the Tennessee Titans on October 18, Welker caught 10 passes for 150 yards, a new career high (at the time), and two touchdowns.

[102] In the Patriots' Week 14 win at home against the Carolina Panthers, Welker caught 10 passes (out of 19 total completions for Brady) for 105 yards.

In a Week 17 loss to the Houston Texans, Welker suffered a knee injury after getting hit by Bernard Pollard in the first quarter while running upfield to make his only reception of the game.

[107] He suffered a torn MCL and ACL in his left knee and was unable to participate in the Patriots' Wild Card Round loss to the Baltimore Ravens.

[111][112] He was also selected to represent the AFC in the Pro Bowl for the second consecutive year, and, for the first time in his career, was named to the All-Pro First Team.

Late in the fourth quarter with a little over four minutes remaining, with the Patriots ahead 17–15 and on the Giants' 44-yard line, Welker dropped a pass with both hands on the ball.

[147] He ended the season tied with Chicago Bears receiver Brandon Marshall for second in receptions with 118, behind Detroit's Calvin Johnson.

[155] With New England, Welker played in two Super Bowls (XLII and XLVI), falling short to the New York Giants each time.

[157] In his debut with the Broncos, Welker had nine receptions for 67 yards and two touchdowns in the 49–27 victory over the Baltimore Ravens on NBC Sunday Night Football.

[163] On December 30, the day after Denver's 34–14 victory over the Oakland Raiders, head coach John Fox announced that Welker was cleared to play in the Broncos's Divisional Round playoff game against the San Diego Chargers on January 12, 2014.

[165] On January 19, Welker earned his third AFC Championship win and Super Bowl appearance after he helped the Broncos defeat his former team, the New England Patriots, 26–16.

Welker made his season debut in Week 3, a 26–20 overtime loss to the Seattle Seahawks in a rematch of the previous year's Super Bowl.

[172][173] In a Week 5 game against the Arizona Cardinals on October 5, Welker passed Rod Smith for the most receptions by an undrafted player in NFL history.